U.S. patent application number 12/681111 was filed with the patent office on 2010-11-18 for mobile communication system, base station, mobile station, and base station installation method.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Futoshi Katada, Nariaki Kishishita, Keiji Okamoto, Taisei Suemitsu, Kuniyuki Suzuki.
Application Number | 20100291931 12/681111 |
Document ID | / |
Family ID | 40590935 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100291931 |
Kind Code |
A1 |
Suemitsu; Taisei ; et
al. |
November 18, 2010 |
MOBILE COMMUNICATION SYSTEM, BASE STATION, MOBILE STATION, AND BASE
STATION INSTALLATION METHOD
Abstract
In a mobile communication system, a mobile station is configured
to obtain data quality information, and provides the obtained data
quality information to a base station A when it is quality
information about data from the base station A, and provides the
data quality information to a base station B when it is quality
information about data from the base station B. The base stations A
and B are configured to provide a base station host apparatus with
the quality information from the mobile station as historical
information about the mobile station, and the base station host
apparatus is configured to compare the pieces of quality
information sent from the two base stations, select one base
station with better quality, instructs it to communicate with the
mobile station, and instructs the other not to communicate with the
mobile station.
Inventors: |
Suemitsu; Taisei; (Tokyo,
JP) ; Suzuki; Kuniyuki; (Tokyo, JP) ;
Kishishita; Nariaki; (Tokyo, JP) ; Katada;
Futoshi; (Tokyo, JP) ; Okamoto; Keiji; (Tokyo,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
40590935 |
Appl. No.: |
12/681111 |
Filed: |
October 27, 2008 |
PCT Filed: |
October 27, 2008 |
PCT NO: |
PCT/JP08/69424 |
371 Date: |
April 1, 2010 |
Current U.S.
Class: |
455/436 |
Current CPC
Class: |
H04W 36/245
20130101 |
Class at
Publication: |
455/436 |
International
Class: |
H04W 36/00 20090101
H04W036/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2007 |
JP |
2007-283621 |
Claims
1. A mobile communication system comprising a mobile station, a
base station, and a base station host apparatus, said mobile
station providing said base station as historical information with
any of information about communication quality between said mobile
station and said base station, information about behavior of said
mobile station, information about communication condition between
said mobile station and said base station, and information about
handover of said mobile station, and on the basis of said
historical information, said base station, or said base station
host apparatus that received said historical information through
said base station, giving an instruction for specifying of a
handover destination for said mobile station or for beam control
for said base station.
2. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
quality, and said information about communication quality includes
information about a reception level at said mobile station.
3. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
quality, and said information about communication quality includes
information about an estimated transmission path characteristic
(CIR) indicating a degree of distortion of a received signal
measured in said mobile station.
4. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
quality, and said information about communication quality includes
information about a ratio between a reception level and
interference power (SIR) measured in said mobile station.
5. The mobile communication system according to claim 1, wherein
said historical information is said information about behavior of
said mobile station, and said information about behavior of said
mobile station includes information about a direction of movement
of said mobile station.
6. The mobile communication system according to claim 1, wherein
said historical information is said information about behavior of
said mobile station, and said information about behavior of said
mobile station includes information about a speed of movement of
said mobile station.
7. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
condition, and said information about communication condition
includes information about a transmission rate of a signal received
from said base station.
8. The mobile communication system according to claim 1, wherein
said historical information is said information about handover of
said mobile station, and said information about handover of said
mobile station includes information indicating that said mobile
station was handed over not to an expected handover destination
base station but to another base station.
9. The mobile communication system according to claim 1, wherein
said historical information is said information about handover of
said mobile station, and said information about handover of said
mobile station includes information indicating that said mobile
station could not transfer to a handover destination base station
and communication with a handover origin base station was
disconnected.
10. The mobile communication system according to claim 1, wherein
said historical information is said information about handover of
said mobile station, and said information about handover of said
mobile station includes information indicating that said mobile
station could not transfer to a handover destination base station
and returned to communication with a handover origin base
station.
11. The mobile communication system according to claim 1, wherein
said base station has a log output function of externally
outputting said historical information as a log.
12. The mobile communication system according to claim 1, wherein
said base station host apparatus has a log output function of
externally outputting said historical information as a log.
13. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
quality, and said information about communication quality includes
information about a degree of reduction of a reception level at
said mobile station with respect to a speed of movement of said
mobile station.
14. The mobile communication system according to claim 2, wherein,
on the basis of said historical information, said base station or
said base station host apparatus controls increase/decrease of the
number of antenna branches used by a base station communicating
with said mobile station.
15. The mobile communication system according to claim 14, wherein
said base station or said base station host apparatus controls the
increase/decrease of said number of antenna branches by using a
table in which said reception level is divided into a plurality of
levels and said number of antenna branches is set in association
with the levels, and said table is set such that said number of
antenna branches becomes larger as said reception level becomes
smaller, and said number of antenna branches becomes smaller as
said reception level becomes larger.
16. The mobile communication system according to claim 7, wherein
said base station or said base station host apparatus instructs
said mobile station such that a base station whose said
transmission rate is the largest is a handover destination.
17. The mobile communication system according to claim 7, wherein
said base station or said base station host apparatus gives an
instruction for beam control such that a base station whose said
transmission rate is the largest directs beam to said mobile
station.
18. The mobile communication system according to claim 1, wherein
when said mobile station is communicating with a plurality of base
stations, said historical information is said information about
communication condition, and said information about communication
condition includes information about the numbers of unoccupied
resources in communications respectively between said plurality of
base stations and said mobile station, and wherein said base
station or said base station host apparatus dynamically adjusts
assignment of said numbers of unoccupied resources on the basis of
said information about the numbers of unoccupied resources.
19. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
condition, and said information about communication condition
includes information about the number of resources of communication
between said base station and said mobile station and information
about a transmission rate of a signal received from said base
station, and wherein, when said number of resources and said
transmission rate both decreased, an instruction is given for beam
control such that beam is directed to said mobile station, and when
said number of resources and said transmission rate both increased,
the base station communicating with said mobile station is
specified as a handover destination.
20. The mobile communication system according to claim 1, wherein
said historical information is said information about communication
condition, said information about communication condition is the
number of error data of cyclic redundancy check (CRC) after channel
decoding in the mobile station, and said base station or said base
station host apparatus calculates a transmission rate of a
reception signal from said number of error data.
21. A mobile communication system comprising a mobile station, a
base station, and a base station host apparatus, said mobile
station providing said base station as historical information with
information about a fading environment where said mobile station is
placed, and on the basis of said historical information, said base
station, or said base station host apparatus receiving said
historical information through said base station, giving an
instruction for specifying of a handover destination for said
mobile station or for beam control for said base station.
22. The mobile communication system according to claim 21, wherein
said information about a fading environment is inputted by a user
through said mobile station.
23. The mobile communication system according to claim 21, further
comprising a local server that provides said mobile station with
said information about a fading environment where said mobile
station is placed, wherein said mobile station receives said
information about a fading environment and provides said
information about a fading environment to said base station.
24. The mobile communication system according to claim 23, wherein
said local server stores said information about a fading
environment of a place where said local server itself is placed,
and when said mobile station enters its communication area, said
local server provides said information about a fading environment
to said mobile station.
25. A mobile communication system comprising a mobile station and a
plurality of base stations, said mobile station being capable of
communicating simultaneously with said plurality of base stations,
said mobile station transmitting/receiving data by using different
sub-carriers to and from said plurality of base stations.
26. The mobile communication system according to claim 25, wherein
when said mobile station receives data from said plurality of base
stations, said mobile station receives multiple divided data from
said plurality of base stations with radio channel formats, and
when said mobile station performs channel decoding inside, said
mobile station couples the respective data portions into one data
piece, and when said mobile station transmits data to said
plurality of base stations, said mobile station divides one piece
of data into a plurality of data pieces, couples the data pieces
with respective control information and applies channel coding, and
transmits the data pieces respectively to said plurality of base
stations.
27. A base station installation method in which a dead spot is
identified by using said log of historical information outputted
from said base station according to claim 11, so as to install a
new base station.
28. A base station installation method in which a dead spot is
identified by using said log of historical information outputted
from said base station host apparatus according to claim 12, so as
to install a new base station.
29. A mobile communication system comprising a mobile station, a
base station, and a base station host apparatus, said base station
or said base station host apparatus providing said mobile station
as historical information with information about communication
quality between said mobile station and said base station or
information about communication condition between said mobile
station and said base station, and on the basis of said historical
information, said mobile station giving an instruction for
specifying of a handover destination for said base station or for
beam control for said base station.
30. A mobile station used for communication with a base station,
said mobile station having a function of providing said base
station as historical information with any of information about
communication quality between said mobile station and said base
station, information about behavior of said mobile station,
information about communication condition between said mobile
station and said base station, and information about handover of
said mobile station.
31. A base station that communicates with the mobile station
according to claim 30, said base station having a function of, on
the basis of said historical information, giving an instruction for
specifying of a handover destination for said mobile station or for
beam control for said base station.
32. A mobile station used for communication with a base station,
said mobile station having a function of providing said base
station as historical information with information about a fading
environment where said mobile station is placed.
33. The mobile station according to claim 32, wherein said mobile
station receives said information about a fading environment where
said mobile station is placed from a local server.
34. A base station that communicates with the mobile station
according to claim 32, said base station having a function of, on
the basis of said historical information, giving an instruction for
specifying of a handover destination for said mobile station or for
beam control for said base station.
35. A mobile station that communicates simultaneously with a
plurality of base stations, said mobile station having a function
of transmitting/receiving data by using different sub-carriers to
and from said plurality of base stations.
36. A base station that communicates with a mobile station, said
base station having a function of providing said mobile station as
historical information with information about communication quality
with said mobile station or information about communication
condition with said mobile station.
37. A mobile station that communicates with the base station
according to claim 36, said mobile station having a function of, on
the basis of said historical information, giving an instruction for
specifying of a handover destination for said base station or for
beam control for said base station.
Description
TECHNICAL FIELD
[0001] The present invention relates to a mobile communication
system in which mobile and base stations communicate with each
other.
BACKGROUND ART
[0002] In mobile communication, as disclosed in Patent Document 1,
for example, there is a scheme in which, when a mobile station
(mobile node) performs a handover by changing the connected base
station, the link bandwidths of the mobile station before and after
the handover are compared and an upper layer discards packets of,
e.g. TCP (Transmission Control Protocol)/RTP (Real-time Transport
Protocol) or adjust the rate. This enables packet handling in
accordance with the upper layer and improves communication
performance during handover.
[0003] Also, as disclosed in Patent Document 2, for example, there
is a scheme in which a home memory station that manages positional
information about terminals is employed to find a particular
terminal moving together with a monitored terminal. This enables
finding a particular terminal moving together with the monitored
terminal.
[0004] Also, as disclosed in Patent Document 3, for example, there
is a scheme in which an emergency center having a positional
information obtaining function and a neighboring information
collecting function is employed to send emergency mail from a
terminal of a person who was involved in an incident/accident to
terminals in the neighborhood. This enables quickly sending
emergency information to neighboring terminals.
[0005] Patent Document 1: Japanese Patent Application Laid-Open No.
2005-348166
[0006] Patent Document 2: Japanese Patent Application Laid-Open No.
2005-286955
[0007] Patent Document 3: Japanese Patent Application Laid-Open No.
2005-222373
DISCLOSURE OF THE INVENTION
[0008] In the scheme disclosed in Patent Document 1, not the mobile
station but the network side merely compares link bandwidths before
and after handover, and there is no information judged from the
terminal's point of view, so that the amount of information for
discarding packets or adjusting rate cannot be very precise.
[0009] Also, in the scheme disclosed in Patent Document 2, the base
station merely manages signals sent from mobile stations to specify
the positions of mobile stations, so that it does not offer the
effects to reduce handover failures and eliminate dead spots.
[0010] Also, in the scheme disclosed in Patent Document 3, even
though an emergency center having a positional information
obtaining function and a neighboring information collecting
function is employed, the emergency center is merely placed in a
particular place, so that dead spots for base stations cannot be
specified in detail, and it does not offer the effects to reduce
dead spots and enable efficient handover.
[0011] The present invention has been made to solve problems as
described above, and an object of the present invention is to
provide a mobile communication system that eliminates dead spots to
allow mobile stations to stably communicate with base stations, and
to provide a mobile communication system that reduces the rate of
handover failures and reduces the number of handovers.
[0012] A first aspect of the mobile communication system according
to the present invention provides a mobile communication system
comprising a mobile station, a base station, and a base station
host apparatus, wherein said mobile station provides said base
station as historical information with any of information about
communication quality between said mobile station and said base
station, information about behavior of said mobile station,
information about communication condition between said mobile
station and said base station, and information about handover of
said mobile station, and wherein, on the basis of said historical
information, said base station, or said base station host apparatus
that received said historical information through said base
station, gives an instruction for specifying of a handover
destination for said mobile station or for beam control for said
base station.
[0013] A second aspect of the mobile communication system according
to the present invention provides a mobile communication system
comprising a mobile station, a base station, and a base station
host apparatus, wherein said mobile station provides said base
station as historical information with information about a fading
environment where said mobile station is placed, and wherein on the
basis of said historical information, said base station, or said
base station host apparatus receiving said historical information
through said base station, gives an instruction for specifying of a
handover destination for said mobile station or for beam control
for said base station.
[0014] A third aspect of the mobile communication system according
to the present invention provides a mobile communication system
comprising a mobile station and a plurality of base stations,
wherein said mobile station is capable of communicating
simultaneously with said plurality of base stations, and wherein
said mobile station transmits/receives data by using different
sub-carriers to and from said plurality of base stations.
Effects of the Invention
[0015] According to the present invention, on the basis of
historical information from a mobile station, a base station or a
base station host apparatus gives instructions for the specifying
of a handover destination for the mobile station or for beam
control for the base station, whereby a mobile communication system
is established which reduces the rate of handover failures and
reduces the number of handovers, and which reduces dead spots to
allow the mobile station to stably communicate with the base
station.
[0016] According to the present invention, a mobile station
transmits/receives different data by using different sub-carriers
to and from a plurality of base stations, whereby a larger amount
of data can be transmitted than when it transmits same data.
[0017] These and other objects, features, aspects and advantages of
the present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] [FIG. 1] A diagram illustrating the configuration of a first
example of the mobile communication system according to a first
preferred embodiment of the present invention.
[0019] [FIG. 2] A diagram illustrating the configuration of a
second example of the mobile communication system according to the
first preferred embodiment of the present invention.
[0020] [FIG. 3] A diagram illustrating the configuration of a third
example of the mobile communication system according to the first
preferred embodiment of the present invention.
[0021] [FIG. 4] A diagram illustrating the configuration of a
fourth example of the mobile communication system according to the
first preferred embodiment of the present invention.
[0022] [FIG. 5] A diagram illustrating the configuration of a fifth
example of the mobile communication system according to the first
preferred embodiment of the present invention.
[0023] [FIG. 6] A diagram illustrating the configuration of a sixth
example of the mobile communication system according to the first
preferred embodiment of the present invention.
[0024] [FIG. 7] A diagram illustrating the configuration of a
seventh example of the mobile communication system according to the
first preferred embodiment of the present invention.
[0025] [FIG. 8] A diagram illustrating the configuration of an
eighth example of the mobile communication system according to the
first preferred embodiment of the present invention.
[0026] [FIG. 9] A diagram illustrating the configuration of a ninth
example of the mobile communication system according to the first
preferred embodiment of the present invention.
[0027] [FIG. 10] A diagram illustrating the configuration of a
tenth example of the mobile communication system according to the
first preferred embodiment of the present invention.
[0028] [FIG. 11] A block diagram illustrating the configuration of
a base station according to the first preferred embodiment of the
present invention.
[0029] [FIG. 12] A block diagram illustrating the configuration of
a mobile station according to the first preferred embodiment of the
present invention.
[0030] [FIG. 13] A diagram illustrating the structure of a data
format of a control channel of a physical channel according to the
first preferred embodiment of the present invention.
[0031] [FIG. 14] A block diagram illustrating the configuration of
a base station host apparatus (network) according to the first
preferred embodiment of the present invention.
[0032] [FIG. 15] A diagram illustrating a method for estimating the
direction of movement of a mobile station on the basis of
historical information.
[0033] [FIG. 16] A diagram illustrating handover failure
history.
[0034] [FIG. 17] A diagram illustrating a method of obtaining a log
of historical information.
[0035] [FIG. 18] A diagram illustrating a method of obtaining a log
of historical information.
[0036] [FIG. 19] A diagram illustrating a method of calculating a
rapid reduction of reception power on the basis of moving speed and
reception power reduction.
[0037] [FIG. 20] A diagram illustrating increasing/decreasing of
the number of antenna branches of a base station.
[0038] [FIG. 21] A block diagram illustrating the configuration of
a base station that increases/decreases the number of antenna
branches on the basis of historical information about a mobile
station.
[0039] [FIG. 22] A diagram illustrating an example of a program for
realizing the judgment operation in the number-of-antenna-branches
determining block.
[0040] [FIG. 23] A diagram illustrating the configuration of a base
station host apparatus that provides instructions to base stations
to increase/decrease the number of antenna branches on the basis of
historical information about mobile stations.
[0041] [FIG. 24] A diagram illustrating the correspondence between
reception level and the number of antenna branches selected in a
base station.
[0042] [FIG. 25] A diagram illustrating a condition in which, on
the basis of transmission rates, the handover destination is
selected to a base station with the largest transmission rate.
[0043] [FIG. 26] A diagram illustrating a condition in which a
handover destination base station is selected on the basis of the
numbers of unoccupied resources,
[0044] [FIG. 27] A diagram illustrating how handover or beam
control is performed as the communication capacity
increases/decreases.
[0045] [FIG. 28] A diagram illustrating a method of calculating
transmission rate.
[0046] [FIG. 29] A diagram showing another example of a
transmission rate calculating method.
[0047] [FIG. 30] A diagram illustrating a screen of a mobile
station through which a user enters the environment where the
mobile station is placed.
[0048] [FIG. 31] A diagram illustrating communication areas of base
stations when a mobile station is in a river.
[0049] [FIG. 32] A diagram illustrating the configuration of a
mobile communication system in which condition notifying servers
input historical information to a mobile station.
[0050] [FIG. 33] A block diagram illustrating the configuration of
a condition notifying server.
[0051] [FIG. 34] A block diagram illustrating the configuration of
a mobile station that receives information from condition notifying
servers and handles it as historical information.
[0052] [FIG. 35] A diagram illustrating a mobile communication
system in which the historical information provided to the base
station side includes high-speed of movement of a mobile
station.
[0053] [FIG. 36] A diagram illustrating a method of estimating
moving speed by detecting notches of fading.
[0054] [FIG. 37] A diagram illustrating a method of detecting
notches of fading.
[0055] [FIG. 38] A diagram illustrating an example of a table used
to judge whether the calculated moving speed is high or not.
[0056] [FIG. 39] A diagram illustrating a mobile communication
system according to a second preferred embodiment of the present
invention.
[0057] [FIG. 40] A diagram illustrating channel coding in which a
mobile station couples data received from base stations into one
data format, in the mobile communication system of the second
preferred embodiment of the present invention.
[0058] [FIG. 41] A diagram illustrating a mobile communication
system according to a third preferred embodiment of the present
invention.
[0059] [FIG. 42] A diagram illustrating operations of a base
station in the mobile communication system of the third preferred
embodiment of the present invention.
[0060] [FIG. 43] A diagram illustrating the configuration of a base
station in the mobile communication system of the third preferred
embodiment of the present invention.
[0061] [FIG. 44] A diagram illustrating the configuration of a
mobile station in the mobile communication system of the third
preferred embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
A. First Preferred Embodiment
[0062] The mobile communication system according to a first
preferred embodiment of the present invention is characterized in
that a mobile station obtains historical information such as
reception level in communications with base stations and provides
the historical information to base stations, whereby the base
station or base station host apparatus (network) side can more
accurately select handover destinations and perform more accurate
beam control, where various examples are possible. Such examples
will be described below.
A-1. First Example
[0063] FIG. 1 illustrates the configuration of a mobile
communication system MC1 according to a first example.
[0064] As shown in FIG. 1, the mobile communication system MC1 has
a network configuration in which a plurality of base stations, such
as a base station 12 and a base station 13, are connected to a base
station host apparatus 14 including base station control equipment
and core network.
[0065] In FIG. 1, a mobile station (=a terminal) 11 is present
between the communication area of the base station 12 (hereinafter
referred to as base station A) and the communication area of the
base station 13 (hereinafter referred to as base station B).
[0066] Now, the base station A can perform wireless transmission
with the mobile station 11, and can also perform wired or wireless
data transmission with the base station host apparatus 14, and the
base station B also has the same functions as the base station
A.
[0067] In the case of W-CDMA (Wideband Code Division Multiple
Access), for example, when the mobile station 11 is in a position
included in both of the communication area of the base station A
and the communication area of the base station B and is trying to
perform a handover between the two base stations, a soft handover
is conducted and the single mobile station is in connection
simultaneously with the two base stations, for example. In the case
of a scheme using hard handover, it is possibly in connection with
either the base station A or the base station B, or it may be
repeatedly performing the operations of making the connection with
the base station A and breaking the connection with the base
station B, and breaking the connection with the base station A and
making the connection with the base station B.
[0068] Next, the operation of the mobile communication system MC1
will be described.
[0069] The mobile station 11 is simultaneously or alternately
performing wireless transmission/reception with the base station A
and the base station B. In this case, the mobile station 11 is
configured such that it receives downlink data from the two base
stations and performs demodulation and decoding, and to thereby
measure characteristics about quality, such as the reception level
of data sent from the base stations, CIR (estimated transmission
path characteristic), SIR (Signal-to-Interference Ratio), etc., and
to capture the characteristics as quality information.
[0070] Then, the mobile station 11 is configured such that, when
the obtained data quality information is about data from the base
station A, it provides the information to the base station A, and
when the obtained data quality information is about data from the
base station B, it provides the information to the base station
B.
[0071] The base station A and the base station B are configured to
provide the quality information, sent from the mobile station 11,
to the base station host apparatus 14 as historical information
about the mobile station 11. Also, the base station host apparatus
14 is configured to then compare the pieces of quality information
sent from the two base stations, select the base station with
better quality and instruct it to communicate with the mobile
station 11 (handover instruction), and to instruct the base station
with inferior quality not to communicate with the mobile station
11.
[0072] Alternatively, the mobile station 11 may be configured such
that it provides the base station A with both of the quality
information about data from the base station A and the quality
information about data from the base station B, as historical
information about the mobile station 11. Alternatively, it may be
configured such that it provides the base station B with both of
the quality information about data from the base station A and the
quality information about data from the base station B, as
historical information.
[0073] Conventionally, the base station side switched handover
destinations by referring to information such as power value of
data received from mobile stations, but the mobile communication
system MC 1 takes the configuration described above and makes it
possible to determine handover destinations and handover timing by
also considering history (reception information) on the mobile
station side, whereby the accuracy of handover is enhanced and
efficient handover is realized.
A-2. Second Example
[0074] FIG. 2 illustrates the configuration of a mobile
communication system MC2 according to a second example. Similarly
to that in FIG. 1, a mobile station 11 is in a place where it is
included in both of the communication area of the base station A
and the communication area of the base station B, and the mobile
station 11 is trying to perform a handover between the two base
stations.
[0075] In the mobile communication system MC2 shown in FIG. 2, a
base station or base station host apparatus 14 does not specify
handover destinations on the basis of historical information from
the mobile station 11; the base station host apparatus 14 is
configured such that, on the basis of historical information from
the mobile station 11, it provides a certain base station with
control information to direct communication beam to the mobile
station 11 so as to include the mobile station 11 in the
communication area, and it provides another base station with
control information not to direct communication beam to the mobile
station 11 so as not to include the mobile station 11 in the
communication area.
[0076] FIG. 2 shows an example in which the base station B is
provided with control information D1 to direct communication beam
to the mobile station 11 so as to include the mobile station 11 in
the communication area, and the base station A is provided with
control information D2 not to direct communication beam to the
mobile station 11 so as not to include the mobile station 11 in the
communication area.
[0077] The base station B provided with the control information D1
performs control to direct communication beam to the mobile station
11 so that the mobile station 11 is included in the communication
area B1 of the base station B. On the other hand, the base station
A provided with the control information D2 does not direct
communication beam to the mobile station 11 and therefore the
mobile station 11 is excluded out of the communication area A1 of
the base station A.
[0078] In this way, in which base station's communication area the
mobile station 11 should be included is determined on the basis of
historical information from the mobile station 11, whereby dead
spots of communication waves can be precisely eliminated.
[0079] "Beam control", like directing beam, means weighting
processing to intensively increase transmission power to the target
mobile station, or to increase reception power from the target
mobile station, by using signal processing techniques such as
adaptive array.
[0080] Also, the base stations may measure the quality of data
transmitted from the mobile station 11 and provide the results to
the base station host apparatus 14 together with the historical
information from the mobile station 11, in which case the
information can be used to determine of which base station's
communication area the mobile station should be included.
A-3. Third Example
[0081] FIG. 3 illustrates the configuration of a mobile
communication system MC3 according to a third example.
[0082] In the mobile communication system MC3 shown in FIG. 3, not
only the base station 12 and the base station 13 but also a base
station 15 (hereinafter referred to as base station C) is connected
to the base station host apparatus 14. The mobile station 11 is
configured to notify base stations of the direction of movement, as
behavior information, of the mobile station 11 as its historical
information. The mobile station 11 is moving toward the base
station B, and it is currently in the communication area of the
base station A and communicating with the base station A. However,
the mobile station 11 is also reaching the communication area of
the base station B and the communication area of the base station
C, and it has a history that it has just slightly communicated with
the two base stations.
[0083] The mobile station 11 keeps the history, and provides the
historical information to the base station A. The base station A
provides the historical information to the base station host
apparatus 14. The base station host apparatus 14 is configured to
process the historical information and obtain the direction of
movement of the mobile station 11, and to give instructions to
effect a handover from the base station A to the base station B
according to the direction of movement.
[0084] That is to say, the base station host apparatus 14 specifies
the base station B as the handover destination, and provides base
station specify information D3 to the base station B and base
station release information D4 to the base station A to release the
communication with the mobile station 11. Receiving the base
station specify information D3, the base station B operates to
direct communication beam to the mobile station 11; the base
station A, receiving the base station release information D3,
operates to cease directing the communication beam to the mobile
station 11. Instead of providing control to direct communication
beam, the base station B receiving the base station specify
information D3 may make resource settings for communication with
the mobile station 11, with macro notification from the
application, for example, and the base station A receiving the base
station release information D4 may forcedly perform operations to
release resources for communication with the mobile station 11,
with macro notification from the application, for example.
[0085] Alternatively, the base station A may be configured such
that, when receiving the historical information, it processes the
historical information to obtain the direction of movement, and
performs operations for a handover to the base station B.
[0086] That is to say, the base station A specifies the base
station B as the handover destination, and gives base station
specify information D3 to the base station B. Receiving the base
station specify information D3, the base station B operates to
direct communication beam to the mobile station 11. Instead of
performing control to direct communication beam, the base station B
receiving the base station specify information D3 may forcedly make
resource settings for communication with the mobile station 11,
with macro notification from the application, for example.
[0087] Thus, when the direction of movement of the mobile station
11 is obtained from its historical information and handover
instructions are thus given, the process only involves one handover
operation to the base station B; this provides the effect to
achieve more efficient handover than conventional schemes in which
handover is repeated.
[0088] That is to say, the mobile station 11 would possibly be
handed over to the base station C when the direction of movement of
the mobile station 11 is not considered; it would be handed over
twice, i.e. once from the base station A to the base station C and
then from the base station C to the base station B, but it is
handed over only once when the direction of movement is
considered.
[0089] In the description above, on the basis of historical
information, the base station side (base station or base station
host apparatus) specifies the handover destination base station;
instead of specifying handover destination, as shown with the
mobile communication system MC2 shown in FIG. 2, the base station
host apparatus 14 may apply beam control to the base stations A and
B such that the mobile station 11 is included in the communication
area of the base station B and the mobile station 11 is not
included in the communication area of the base station A.
A-4. Fourth Example
[0090] FIG. 4 illustrates the configuration of a mobile
communication system MC4 according to a fourth example.
[0091] In the mobile communication system MC4 shown in FIG. 4, the
mobile station 11 is configured to notify base stations of the
speed of movement, as behavior information, of the mobile station
11 as its historical information. The mobile station 11 is moving
from the base station A toward the base station B at high speed,
and the mobile station 11 is in communication only with the base
station. A.
[0092] The mobile station 11 provides information about the speed
of movement to the base station A.
[0093] The base station A gives the historical information to the
base station host apparatus 14. The base station host apparatus 14
is configured such that, when receiving the historical information,
it provides a control signal D5 to the base station A to perform
beam control so as not to exclude the mobile station 11 from the
communication area A1 as long as possible. On the other hand, it
provides a control signal D6 to the base station B to perform beam
control such that the mobile station 11 enters the communication
area B1. Also, a base station or the base station host apparatus 14
gives instructions such that the mobile station 11 is handed over
early from the base station A to the base station B.
[0094] Alternatively, the system may be configured such that the
base station A processes the historical information from the mobile
station 11 and performs beam control such that the mobile station
11 is not excluded from the communication area A1 as long as
possible, and the base station A also instructs the base station B
to perform beam control such that the mobile station 11 enters the
communication area B1.
[0095] Thus, the base station A directs communication beam toward
the mobile station 11 such that it will not go out of the area, and
the base station B is instructed to soon effect a handover, whereby
a sufficient time is ensured for handover even when the mobile
station 11 is moving at high speed.
[0096] In this way, when the mobile station is moving at high
speed, the mobile station 11 notifies the base station side of that
fact, whereby efficient handover is achieved.
[0097] Also, directing beams both from the base station A and the
base station B to the mobile station 11 offers the effect to reduce
dead spots, in addition to facilitating handover.
[0098] The description above illustrated that the mobile station 11
is moving from the base station A toward the base station B at high
speed; in the case of soft handover where a plurality of base
stations are communicating with the mobile station, for example,
all base stations communicating with the mobile station can know
the direction of presence of the mobile station with an algorithm
for radio wave arrival direction estimation, for example. Then, the
base stations can perform control to direct beam to the direction
of arrival of the radio waves, and they can direct beam to the
mobile station even when they are not provided with information
about the direction of movement. The control to direct beam can
thus be achieved even when the mobile station 11 does not provide
moving direction information and positional information.
[0099] However, when information about the direction of movement is
provided, the base stations can know whether or not the mobile
station is moving toward themselves (base stations); then, when the
mobile station is not moving toward themselves, they do not have to
direct beams, and they do not have to perform beam control.
Accordingly, information about the direction of movement can be
included in the historical information together with the speed of
movement. Then, only limited base stations direct beam to the
mobile station, which reduces the amount of processing and saves
power, and minimizes the number of handovers.
[0100] Positional information, as well as information about the
direction of movement, can be employed to allow base stations to
know whether the mobile station is moving toward themselves (base
stations); when the mobile station is not moving toward a base
station, it does not have to direct beam, and does not need beam
control. Accordingly, positional information may be included in the
historical information as well as the speed of movement.
A-5. Fifth Example
[0101] FIG. 5 illustrates the configuration of a mobile
communication system MC5 according to a fifth example.
[0102] In the mobile communication system MC5 shown in FIG. 5, not
only the base station 12 and the base station 13 but also a base
station 15 (base station C) is connected to the base station host
apparatus 14. The mobile station 11 is configured to measure the
transmission rates of data received at the mobile station 11 from
the base stations A to C and provide the information about
communication condition as historical information to the base
stations. The mobile station 11 is communicating simultaneously
with the three base stations A to C; or it is communicating only
with the base station A and it has a history that it communicated
also with the base station B and the base station C in the not far
past (for example, a threshold about time is provided and a time
below that threshold is defined as "not far past"), since it is
also close to the communication areas of the base station B and the
base station C.
[0103] When the mobile station 11 is simultaneously communicating
with the three base stations A to C, the mobile station 11 provides
the individual base stations with the results of measurement of the
transmission rates of data respectively received from the base
stations; alternatively, the results of measurement of the
transmission rates of data from the three base stations are all
provided to a particular one base station. Alternatively, the
results of measurement of the transmission rates of data from the
three base stations may be all provided to all of the base stations
A to C.
[0104] (A-5-1. When Communicating only with One Base Station)
[0105] When the mobile station 11 is communicating only with the
base station A, the mobile station 11 provides the base station A
with the result of measurement of the data transmission rate in the
current communication with the base station A and also with all
results of measurement of the data transmission rates in the past
communications with the base station B or C; alternatively, the
information about the results of measurement of transmission rates
is provided to all of the base stations A to C as historical
information.
[0106] Now, as shown in FIG. 5, the transmission rate with the base
station A is small, the transmission rate with the base station B
is large, and the transmission rate with the base station C is
intermediate between those with the base stations A and B.
[0107] When the base station A, or the base stations A to C,
obtained the information about transmission rate measurement as
historical information, the base station A or the base stations A
to C provide the historical information to the base station host
apparatus 14. The base station host apparatus 14 is configured to
give instructions for a handover from the base station A to the
base station B.
[0108] That is to say, the base station host apparatus 14 specifies
the base station B as the handover destination, and gives base
station specify information D3 to the base station B and gives base
station release information D4 to the base station A to release the
communication with the mobile station 11. Receiving the base
station specify information D3, the base station B performs
resource settings for communication with the mobile station 11,
with macro notification from the application, for example, and the
base station A receiving the base station release information D4
forcedly performs operations to release resources for the
communication with the mobile station 11, with macro notification
from the application, for example.
[0109] Thus, only with one execution, the mobile station 11 can be
handed over to the base station that is expected to offer a larger
transmission rate, which enhances handover efficiency and
efficiency of the entire communication.
[0110] Alternatively, the base station A, receiving the historical
information, may be configured to perform operations for a handover
to the base station B on the basis of the historical information.
Also, a base station other than the base station A may be
configured to give instructions for a handover from the base
station A to the base station B.
[0111] The scheme is effective not only when the base station host
apparatus 14 specifies the handover destination, but also when the
beams of base stations are controlled to reduce dead spots.
[0112] In this case, on the basis of the information about
transmission rates from the mobile station 11, the beam of the base
station B is controlled to be directed to the mobile station 11 to
further stabilize the communication between the mobile station 11
and the base station B offering the largest transmission rate.
[0113] On the other hand, the base station A offering a small
transmission rate is controlled such that it does not direct beam
to the mobile station 11, or no beam directing control is
performed. The same is true for the base station C.
[0114] Thus, as a result, the mobile station 11 can be quickly
handed over from the base station A to the base station B to
perform communication at the largest transmission rate.
[0115] Such beam control instructions may be given by the
individual base stations A to C, or by the base station host
apparatus 14. Thus, the quality of communication between the base
station B and mobile station is further enhanced and the
transmission rate is also increased.
[0116] (A-5-2. When Communicating with all Base Stations)
[0117] Similarly to the description above, also when the mobile
station 11 is in communication simultaneously with all base
stations A to C, the base stations A to C, or the base station host
apparatus 14, is provided with the information about transmission
rates from the mobile station 11 and performs beam control or
specifies the handover destination.
[0118] In this case, when the beam control and the specifying of
the handover destination are conducted in such a way as to allow
the mobile station to communicate only with the base station B and
not with the base stations A and C, the resources of the base
stations A and C can be released to facilitate efficient use of
resources. However, this scheme is effective when the
communications between the base stations A to C and the mobile
station 11 are all exchanging same data.
[0119] When the base station A and the mobile station 11, the base
station B and the mobile station 11, and the base station C and the
mobile station 11, are all sending/receiving different independent
data (or data that will be combined into one piece of data after
received), all base stations perform control to direct beams to the
mobile station 11. This is because larger amounts of data can be
sent/received when the communication is connected with a larger
number of base stations.
A-6. Sixth Example
[0120] FIG. 6 illustrates the configuration of a mobile
communication system MC6 according to a sixth example.
[0121] In the mobile communication system MC6 shown in FIG. 6, not
only the base station 12 and base station 13 but also a base
station 15 (base station C) is connected to the base station host
apparatus 14. The mobile station 11 is configured to provide base
stations with a handover failure history as historical information
indicating that a base station is not an expected handover
destination. The mobile station 11 is in communication with the
base station A, and is moving from within the communication area of
the base station A toward the communication area of the base
station B. In the course of movement, the mobile station 11 enters
not only the communication area of the base station B but also the
communication area of the base station C. The mobile station 11
tried to perform handover to the base station C, but it failed to
handover some times, and it has judged that the base station C was
inappropriate as a handover destination.
[0122] In such a case, the mobile station 11 is configured to
provide the communicating base station A with information as
historical information indicating that the base station C is a
not-expected handover destination.
[0123] Receiving the historical information indicating a
not-expected handover destination, the base station A gives the
historical information to the base station host apparatus 14. The
base station host apparatus 14 is configured to give instructions
to effect a handover not to the base station C as a not-expected
handover destination but to the base station B for which
not-expected handover destination information was not received.
[0124] That is to say, the base station host apparatus 14 specifies
the base station B as the handover destination base station, and
gives base station specify information D3 to the base station B,
and gives base station release information D4 to the base station A
to release the communication with the mobile station 11. Receiving
the base station specify information D3, the base station B
performs resource settings for communication with the mobile
station 11, with macro notification from the application, for
example, and the base station A receiving the base station release
information D4 forcedly performs operations to release the
resources for communication with the mobile station 11, with macro
notification from the application, for example.
[0125] Alternatively, the base station A, who received the
historical information, may perform handover operations to the base
station B on the basis of the historical information.
[0126] Using such historical information makes it possible to
reduce the number of handovers and to facilitate efficient
handover.
[0127] That is to say, when the mobile station 11 does not provide
the not-expected handover destination information to the base
station side, then the mobile station 11 might be handed over
twice, i.e. from the base station A to the base station C, and next
from the base station C to the base station B as it further moves
toward the base station B; however, it is handed over only once
when the scheme of this example is adopted.
[0128] Now, whether a not-expected handover destination or not is
determined according to whether handover to the base station has
failed a predetermined number of times. For example, when the
criterion of judgment is "twice", and when the mobile station 11 is
moving, as shown in FIG. 6, from within the communication area of
the base station A into the communication area of the base station
B and reaches the communication area of the base station C in the
course of movement, the mobile station 11 judges the base station C
as a not-expected handover destination if an attempt for a handover
to the base station C failed, e.g. it was connected but soon
disconnected, twice.
[0129] Then, the information as a not-expected handover destination
is stored in the mobile station 11 for a given period, and it is
provided to the communicating base station A as historical
information. However, when the base station C is the only candidate
for handover destination, handover is made to the base station
C.
[0130] Handover failures can be reduced when base stations that are
even slightly more likely to succeed in handover are thus specified
as handover destinations.
A-7. Seventh Example
[0131] FIG. 7 illustrates the configuration of a mobile
communication system MC7 according to a seventh example.
[0132] In the mobile communication system MC7 shown in FIG. 7, not
only the base station 12 and base station 13 but also a base
station 15 (base station C) is connected to the base station host
apparatus 14. The mobile station 11 is configured to provide a
handover failure history to base stations as historical
information, in the example of FIG. 7, the handover failure history
further includes information indicating that the communication with
the connected base station was also disconnected. Now, the mobile
station 11 is communicating with the base station A, and is moving
in the middle between the base station B and the base station C.
Accordingly, it is reaching the communication areas of both of the
base station C and the base station B, and it first tried to make a
handover to the base station C, e.g. because the transmission power
from the base station C was larger, but the communication was
disconnected and the handover failed. Also, the communication with
the base station A, as the handover origin, was also
disconnected.
[0133] In such a case, the mobile station 11 stores, in itself for
a given period, not only the information that it could not transfer
to the communication with the base station C as the handover
destination but also the information that the communication with
the base station A as the handover origin was also broken and it
could not return to the handover origin.
[0134] Then, when it is re-connected to some base station (the base
station A in the example of FIG. 7), it gives the stored handover
failure history as historical information to the reconnected base
station A. The base station A provides the historical information
to the base station host apparatus 14. The base station host
apparatus 14 is configured such that, on the basis of the handover
failure history, it gives instructions to hand over to the base
station B, not to the base station C who failed in handover.
[0135] That is to say, the base station host apparatus 14 specifies
the base station B as the handover destination base station, and
provides base station specify information D3 to the base station B,
and provides base station release information D4, for releasing
communication with the mobile station 11, to the base station A.
Receiving the base station specify information D3, the base station
B performs resource settings for communication with the mobile
station 11, with macro notification from the application, for
example, and the base station A receiving the base station release
information D4 forcedly performs operations to release the
resources for the communication with the mobile station 11, with
macro notification from the application, for example.
[0136] Alternatively, the base station A., who received historical
information, may be configured to perform handover operations to
the base station B on the basis of the historical information.
[0137] Thus, by using such historical information, the base station
B who has no failure history is specified as the handover
destination, and handover failures are reduced.
[0138] Alternatively, in placed of the configuration in which the
base station host apparatus 14 specifies the base station B as the
handover destination, the base stations B and C may voluntarily
perform beam control (or the base station host apparatus 14 applies
beam control to the base stations B and C) such that the base
station B directs beam to the mobile station 11 and the base
station C does not direct beam to the mobile station 11 (or it
directs "null" to the mobile station 11), whereby the mobile
station 11 is more likely to be handed over not to the base station
C but to the base station B.
[0139] In this case, the mobile station 11 is more likely to be
handed over to the base station B, than to the base station C that
is likely to fail in handover, and handover failures are reduced;
also, the shapes of the communication areas are varied so that the
normal communication can be continued, and it substantially offers
the effect to reduce dead spots.
[0140] In radio waves sent from antennas, or in the beam patterns
of radio waves received at antennas, portions where the electric
field strength of beam extremely falls are called "null", and
"directing null" means to direct such a portion to the mobile
station.
A-8. Eighth Example
[0141] FIG. 8 illustrates the configuration of a mobile
communication system MC8 according to an eighth example.
[0142] In the mobile communication system MC8, as in the mobile
communication system MC7 described with FIG. 7, the mobile station
11 is configured to provide a handover failure history to base
stations as historical information. In the example of FIG. 8, the
handover failure history further includes information indicating
that it failed to handover to the base station C and returned to
the communication with the connected base station A (the
communication with the base station A was continued). The mobile
station 11 is communicating with the base station A, and is moving
in the middle between the base station B and the base station C.
Accordingly, the mobile station 11 is reaching the communication
areas of both of the base station C and the base station B, and it
tried to handover to the base station C in the past (within a given
time period), because, e.g. the transmission power from the base
station C was larger, but the communication was disconnected and
the handover failed, and it is continuously communicating with the
base station A.
[0143] In such a case, the mobile station 11 provides the base
station A with the handover failure history as historical
information indicating that it has failed to hand over to the base
station C in the past and returned to the communication with the
base station A. The base station A provides the historical
information to the base station host apparatus 14. On the basis of
the handover failure history, the base station host apparatus 14
gives instructions to effect a handover to the base station B, not
to the base station C who has failed in handover.
[0144] Alternatively, the base station A, who received historical
information, may be configured to perform handover operations to
the base station B on the basis of the historical information.
[0145] Thus, by using such historical information, the base station
B who has no failure history is specified as the handover
destination, and handover failures are reduced.
[0146] Alternatively, in placed of the configuration in which the
base station host apparatus 14 specifies the base station B as the
handover destination, the base stations B and C may voluntarily
perform beam control (or the base station host apparatus 14 applies
beam control to the base stations B and C) such that the base
station B directs beam to the mobile station 11 and the base
station C does not direct beam to the mobile station 11 (or it
directs "null" to the mobile station 11), whereby the mobile
station 11 is more likely to be handed over not to the base station
C but to the base station B.
[0147] In this case, the mobile station 11 is more likely to be
handed over to the base station B, than to the base station C that
is likely to fail in handover, and handover failures are reduced;
also, the shapes of the communication areas are varied so that the
normal communication can be continued, and it substantially offers
the effect to contribute to the reduction of dead spots.
A-9. Ninth Example
[0148] FIG. 9 illustrates the configuration of a mobile
communication system MC9 according to a ninth example
[0149] In the mobile communication system MC9, a base station 12
(base station C) is connected to a base station host apparatus 14.
The mobile station 11 is configured to measure the reception level
of received data and provides the base station A with the
measurement information as historical information about signal
quality, e.g. about whether the reception level is good or bad.
[0150] The base station gives the historical information to the
base station host apparatus 14. On the basis of the historical
information, the base station host apparatus 14 provides control
information D1 such that the base station A directs beam to the
mobile station 11 to include the mobile station 11 in the
communication area.
[0151] On the basis of the control information D1, the base station
A raises the reception level by directing beam to the mobile
station 11.
[0152] Thus, the base station A can more accurately direct beam to
the mobile station 11 by using the reception level measurement
information at the mobile station 11 as historical information,
whereby the mobile station 11 can more stably stay in the
communication area of the base station A.
A-10. Tenth Example
[0153] FIG. 10 illustrates the configuration of a mobile
communication system MC10 according to a tenth example.
[0154] In the mobile communication system MC10, as in the mobile
communication system MC9 described with FIG. 9, measurement
information about the reception level at the mobile station 11 is
used as historical information; however, in the mobile
communication system MC10, the base station A is configured to
judge the historical information by itself and direct beam to the
mobile station 11, while, in the mobile communication system MC9,
the base station host apparatus 14 gives instructions to the base
station A to direct beam to the mobile station 11.
[0155] Thus, the base station A itself makes the decision, and so
the delay of time required by the communication from the base
station A to the base station host apparatus 14 is eliminated, and
the beam can be directed to the mobile station 11 more quickly than
when the base station host apparatus 14 provides control.
A-11. Configuration of Base Stations
[0156] Next, referring to the block diagram of FIG. 11, the
configuration of the base stations A to C used in the mobile
communication systems MC1 to MC10 explained with FIGS. 1 to 10 will
be described.
[0157] As shown in FIG. 11, the base station chiefly includes an
antenna AT1 (antenna branch), a radio section RX1 for receiving and
transmitting analog signal, an A/D converter 101, a D/A converter
108, and a data processor block 100.
[0158] The data processor block 100 includes a demodulator 102, a
decoder 103, a historical information obtaining block 104, an
analyzer 105, an encoder 106, a modulator 107, and a beam forming
block 109.
[0159] For example, the historical information obtaining block 104
and the analyzer 105 are formed of CPU (Central Processing Unit),
DSP (Digital Signal Processor), or FPGA (Field Programmable Gate
Array), and the decoder 103, the encoder 106, and the beam forming
block 109 are formed of DSP or FPGA, or both.
[0160] In the radio section RX1, analog data received at the
antenna AT1 is down-converted from radio frequencies (around 2 GHz
in the case of W-CDMA) to the baseband range (e.g. 16 MHz) to
become a baseband signal, which is given to the A/D converter 101
and converted from analog data to digital data.
[0161] The digital data is demodulated in the demodulator 102
(which also performs OFDM (Orthogonal Frequency Division
Multiplexing) demodulation using fast Fourier transform), and DPDCH
(Dedicated Physical Data Channel) and DPCCH (Dedicated Physical
Control Channel) are reproduced in the case of a physical channel
(W-CDMA (3GPP TS25.211).
[0162] In this process, one like a control channel (DPCCH in the
case of W-CDMA) is multiplexed in the physical channel, and the
historical information from the mobile station is contained in that
channel. The historical information obtaining block 104 extracts
that historical information, and the analyzer 105 specifies the
historical information, e.g. by referring to a table. Then, the
beam forming block 109 calculates weighting factors to be
multiplied with data for individual antenna branches. The
calculated weighting factors are multiplied in the modulator 107.
The D/A converter 108 converts the data after multiplication into
analog data, and the radio section RX1 up-converts the data, which
is transmitted from the antenna AT1 at radio frequencies.
[0163] The method of calculating the weighting factors uses an
algorithm such as LMS (Least Mean Square), RLS (Recursive Least
Mean) as described in "Adaptive Signal Processing with Array
Antennas (written by Nobuyoshi Kikuma and published from Kagaku
Gijutsu Shuppan, Inc.), for example.
[0164] The weighting factors are used for beam control; for
example, the intact calculated factors are employed to direct beam
to the mobile station, and the weighting factors are invalidated
(all "1") when not directing beam.
[0165] When historical information is contained not in the control
channel of a physical channel (DPCCH in the case of W-CDMA) but in
the transport channel after channel decoding (DTCH (Dedicated
Traffic Channel), DCCH (Dedicated Control Channel) in the case of
W-CDMA), the historical information obtaining block 104 extracts
the historical information contained in the data decoded in the
decoder 103, and the analyzer 105 specifies it.
[0166] After the historical information has been obtained, the data
may be sent as messages to the base station host apparatus
separately from data, or may be sent to the host apparatus in the
form contained in data, in which case the historical information is
extracted by a function corresponding to the historical information
obtaining block in the host apparatus. In this case, the historical
information about the mobile station is processed in the base
station host apparatus.
[0167] The decoder 103 is a functional block that performs
so-called L2 processing and channel decoding, and it applies
upper-layer processing to demodulated data and provides it to the
base station host apparatus or the historical information obtaining
block 104.
[0168] "L2 processing" is processing in Layer 2. Specifically, it
includes processing such as MAC (Media Access Control), RLC (Radio
Link Control), PDCP (Packet Data Convergence Protocol) and so
forth.
[0169] The L2 processing and channel decoding are not described in
detail herein because they are conventional operations.
[0170] The encoder 106 is a functional block that performs L2
processing and channel coding, which applies L2 processing and
channel coding to downlink data given from the base station host
apparatus.
[0171] The modulator 107 modulates data encoded in the encoder 106,
according to a modulation scheme such as QPSK (Quadrature Phase
Shift Keying) or 16QAM (Quadrature Amplitude Modulation), or
64QAM.
[0172] In the processing in the modulator 107, when transmission
data is branched to individual antenna branches, the weighting
factors for individual branches calculated in the beam forming
block 109 are multiplied for individual branches.
A-12. Configuration of Mobile Station
[0173] Next. Referring to the block diagram of FIG. 12, the
configuration of the mobile station 11 used in the mobile
communication systems MC1 to MC10 explained with FIGS. 1 to 10 will
be described.
[0174] As shown in FIG. 12, the mobile station chiefly includes an
antenna AT2, a radio section RX2 for receiving and transmitting
analog signal, an A/D converter 201, a D/A converter 208, and a
data processor block 200.
[0175] The data processor block 200 includes a demodulator 202, a
decoder 203, a historical information storage block 204, a
measurement block 205, an encoder 206, and a modulator 207.
[0176] The decoder 203 and the encoder 206 are formed of DSP or
FPGA, or both, and the historical information storage block 204 is
formed of memory.
[0177] Analog data received at the antenna AT2 is down-converted in
the radio section RX2 from radio frequencies to the baseband range
to become a baseband signal, and is given to the A/D converter 201
and converted from analog data to digital data.
[0178] The digital data is demodulated in the demodulator 202
(which also performs OFDM demodulation using fast Fourier
transform), and the demodulated data undergoes channel decoding and
upper-layer processing such as L2 processing in the decoder
203.
[0179] During demodulation in the demodulator 202, reception level,
SIR etc. are measured.
[0180] Also, data is channel-decoded in the decoder 203, and, in
the case of W-CDMA, for example, the number of OKs (no-error data)
(or the number of NGs (error data)) of the results of CRC (Cyclic
Redundancy Checking) attached to TBs (Transport Blocks) is counted.
In the measurement block 205, the results of such measurement are
converted to a historical information format (when reception level
or SIR has a 8-bit width such as -127 to +127, data is divided into
levels and contained in 2 bits, for example), which is stored in
the historical information storage block 204. In the modulator 207,
the historical information is inserted into the control channel of
a physical channel (which corresponds to DPCCH in the case of
W-CDMA).
[0181] FIG. 13 shows an example of the position of insertion of the
historical information.
[0182] FIG. 13 illustrates a channel format where the historical
information is inserted in the control channel of a physical
channel. In FIG. 13, the ninth to fifth bits of 0-origin are a
known sequence (Pilot bits) E4. The fourth to third bits are data
format kind information (corresponding to TFCI in W-CDMA) E3. The
second to first bits are the historical information E2. The zeroth
bit is transmission power control information (which corresponds to
TPC bit in W-CDMA) E1. In the 2-bit region for historical
information, the information is defined for example as 00:
reception level is low, 01: one handover failure with base station
A, and so on. Defining the historical information with fewer bits
reduces the loads in the analysis in base stations or base station
host apparatus (network) and enables high-speed processing.
[0183] Alternatively, the historical information may be inserted in
data in the encoder 206 or during upper-layer processing (which
corresponds to DCCH, DTCH in W-CDMA).
[0184] The data in which historical information is inserted is
given from the modulator 207 to the D/A converter 208 and converted
to analog signal, up-converted in the radio section RX2, and
transmitted from the antenna AT2 as a radio frequency signal.
[0185] While FIG. 12 shows a single antenna AT2, it may include
multiple antennas. Multiple branches are required in the case of
MIMO (Multiple Input Multiple Output).
A-13. Configuration of Base Station Host Apparatus
[0186] Next, referring to the block diagram of FIG. 14, the
configuration of the base station host apparatus used in the mobile
communication systems MC1 to MC10 explained with FIGS. 1 to 10 will
be described.
[0187] As shown in FIG. 14, the base station host apparatus
includes a historical information accumulating block 301, an
analyzer 302, and a controller 303.
[0188] When the base station host apparatus receives historical
information (measurement information) from a base station as
messages or in the form contained in data, the historical
information accumulating block 301 extracts and stores the
historical information, and the analyzer 302 analyzes the contents
of the historical information. Then, on the basis of the contents
of the historical information, the controller 303 generates
instructions for operations that the base station should
perform.
[0189] For example, suppose that a mobile station is communicating
with the base station A and can be handed over either to the base
station B or the base station C; then, if it received a handover
failure history about the base station C as historical information,
then, on the basis of the historical information, it gives
instructions to the base stations A to C to effect a handover to
the base station B. This reduces the possibility of handover
failures.
[0190] Or, for example, it gives instructions to the base station B
for beam control to direct beam to the mobile station, and to the
base station C for beam control not to direct beam to the mobile
station. This reduces dead spots.
[0191] Or, for example, when the mobile station is communicating
with the base station A and is also included in the communication
areas of the base station B and the base station C, and when the
reception level of the current communication with the base station
A exhibits a low value, the reception level of past communication
with the base station B exhibits a high value, and the reception
level of past communication with the base station C exhibits a low
value, then the base station host apparatus receives the historical
information about individual base stations sent from the mobile
station and gives instructions to the base stations A and B to
effect a handover from the base station A to the base station B, or
it gives instructions to the base station B to direct beam to the
mobile station 11, and to the base station C not to direct beam to
the mobile station (or direct null), so as to promote a handover
from the base station A to the base station B.
[0192] This stabilizes the communication because the mobile station
can be quickly handed over to the base station B that is capable of
offering more stable communication. The handover can be achieved
efficiently and dead spots are reduced.
A-14. Judgment Operation in Measurement Block of Mobile Station
[0193] Next, referring to FIG. 15, an example of the judgment
operation in the measurement block 205 of the mobile station
explained with FIG. 12 will be described.
[0194] FIG. 15 shows a history table illustrating the judgment
operation in the measurement block 205 where history information
from the mobile station includes the direction of movement of the
mobile station, which illustrates the judgment operation in the
mobile communication system MC3 shown in FIG. 3.
[0195] The mobile station 11 holds histories about the base
stations A, B and C, and it judges whether it is moving closer to
or away from the base stations on the basis of variations of
parameters such as reception level, CIR (estimated transmission
path characteristic) and SIR.
[0196] The following information can be seen from the table shown
in FIG. 15.
[0197] The reception level of the base station (shown as BTS) A
became larger, its OR became smaller, and its SIR became
smaller.
[0198] The reception level of the base station B became smaller,
CIR became smaller, and SIR became larger.
[0199] The reception level of the base station C became smaller,
CIR became larger, and SIR became larger.
[0200] From the information, it is judged that the mobile station
11 is moving closer to the base station A, moving away from the
base station C, and moving slightly away from the base station B.
The mobile station 11 provides the information as historical
information to the base station currently in communication.
[0201] When the history table is structured in two layers, like a
short time-width (e.g. 1 ms) history and a long time-width (e.g. 1
second) history, the base stations can be informed of mobile
station's short-cycle behavior and long-cycle behavior. For
example, when the mobile station is moving in a serpentine way from
the base station C toward the base station A, or when it goes out
from behind a building, the SIR of the base station C temporarily
becomes larger and the mobile station may be judged on the basis of
the short-time history as if moving closer to the base station C;
however, on the basis of the long-time history, SIR of the base
station C is gradually becoming smaller and it shows that the
mobile station is moving from the base station C toward the base
station A.
[0202] Thus, by forming the table in a layered structure,
influences of obstacles, as are often the case in mobile
communications, can be considered in order to allow the base
stations to more accurately know the behavior of the mobile
station. The structure of the history table is not limited to
2-layered structure, but it can be 3-layered, and such a
multi-layered structure allows the mobile station to inform base
stations about its behavior in more detail.
[0203] By using multi-layered histories, base stations can also
perform long-cycle and short-cycle power control. That is to say,
it is possible to control +1 dB per 20 ms while controlling .+-.1
dB per 1 ms (control to vary power transmitted from the base
station to the mobile station and control in which the base station
raises and lowers power transmitted from the mobile station to the
base station). This enables radio communications to keep more
precise quality.
[0204] Thus, generating historical information in a table reduces
circuit scale, the amount of memory, and the amount of processing.
The bottom section in the table of FIG. 15 shows an example of
weightings for individual parameters, where 3 is multiplied for
reception level, 4 for CIR, and 5 for SIR.
[0205] CIR indicates the degree of signal distortion in radio
transmission. It is obtained by calculating distortion on the basis
of known sequence data sent/received between mobile and base
stations, for example.
[0206] For example, with a know sequence 1+0.times.j, 1+0.times.j,
1+0.times.j, 1+0.times.j (j: complex number, represented in the
form I component+Q component.times.j), when the base station sends
out downlink data and the mobile station receives the data through
radio transmission path and extracts that known sequence data as
1.2+0.3.times.j, 1.1+0.5.times.j, 0.9+0.3.times.j, 1.4+0.2.times.j,
then the mean is 1.15+0.325.times.j and this is the degree of
distortion from 1+0.times.j.
[0207] SIR is the ratio between signal power and interference
power. For example, it can be obtained by using known sequence data
as described above and checking its variations. Specifically, it
can be obtained by obtaining the scattering of received known
sequence data as the interference level, and obtaining a sum of
"the square of sum of real parts (I components)" and "the square of
sum of imaginary parts (Q components)" of the received known
sequence data as the signal level, and calculating signal
level/interference level.
[0208] Another example of the judgment operation in the measurement
block 205 of the mobile station will be described referring to FIG.
16.
[0209] FIG. 16 shows a table illustrating the judgment operation in
the measurement block 205 where history information from the mobile
station is mobile station's handover failure history, and it
illustrates the judgment operation in the mobile communication
systems MC6 to MC8 described with FIGS. 6 to 8.
[0210] The mobile station 11 is in the service areas of the three
base stations A, B and C, and the mobile station 11 is currently
communicating with the base station A.
[0211] In the table of FIG. 16, handover is shown as "HO", and for
individual base stations the table shows the number of HO failures,
the number of communication disconnections, the number of HOs to
third BTS, and the number of returns to HO origin.
[0212] In FIG. 16, "disconnect: 1" means that a handover to another
base station failed once and the current communication with a base
station was disconnected. The column "failure" shows the total
number of failures, and the failure history in this case is
"1".
[0213] Also, "HO to third BTS" means that a handover was made to a
not-expected third base station.
[0214] Also, "return to HO origin" means that a handover to a
handover destination could not be achieved and returned to the
communication with the originally communicating base station.
[0215] As shown in FIG. 16, for the base station C, the section "HO
to third BTS" shows a history "1" and the section "return to HO
origin" shows a history "2". This means that the mobile station 11
was handed over once to the not-expected handover destination base
station C, and that it failed to hand over to the base station C
twice and returned to the communication with the original base
station A. The failure history is "3" in this case.
[0216] The base station B has no handover failure history, though
the mobile station is in its communication area. This can be
effective information indicating that, when the mobile station
moves from the base station A toward the base stations B and C, it
should be handed over not to the base station C but to the base
station B.
[0217] With this history, a base station or base station host
apparatus gives instructions to the base station B to direct the
beam to the mobile station 11. The mobile station 11 can thus be
efficiently handed over to the base station B that is less likely
to fail to establish a handover than other base stations.
[0218] As to the history, the three factors in the table may be
associated with values and sent to base stations, or not the
factors but only the number of failures for each base station may
be associated with value and sent to base stations.
A-15. Another Example of Usage of Historical Information
[0219] The description above has illustrated configurations in
which historical information from the mobile station is employed to
select a handover destination or to perform beam control, but the
historical information may be employed to install base stations,
where historical information from the mobile station is employed to
find dead spots and install base stations there (or to take
measures such that the radio waves from existing base stations
reach there). A configuration for this purpose will be described
referring to FIG. 17.
[0220] As shown in FIG. 17, a base station BS has a log output
function and it outputs historical information sent from a mobile
station MS as a log.
[0221] The mobile station MS receives data from the base station BS
and sends historical information indicating, e.g. reception power
is low, to the base station. The base station BS receives it and
outputs it as a log.
[0222] The log outputted from the base station BS is collected by a
separately provided log collecting apparatus LS, and dead spots can
be reduced by raising the transmission power of an existing base
station to raise the reception power at the mobile station. Also,
the collected log can be employed to find dead spots and install
new base stations.
[0223] Also, FIG. 18 shows a configuration in which a base station
host apparatus OBS is equipped with a log output function, where
the base station host apparatus OBS receives history information
from the mobile station MS via the base station BS and outputs it
as a log.
[0224] In this case, the log outputted from the base station host
apparatus OBS is collected by a separately provided log collecting
apparatus LS, and dead spots can be reduced by raising the
transmission power of an existing base station to raise the
reception power at the mobile station. Also, the collected log can
be employed to find dead spots and install new base stations.
[0225] The operation of collecting logs is thus performed not for
each base station BS but for each base station host apparatus OBS
that manages base stations BS, and the user as an analyzer can save
time to collect logs.
[0226] The log output function provided in the base station BS and
the base station host apparatus OBS can be realized with a
configuration in which log output circuitry is provided in FPGA and
historical information is outputted to a certain connector of the
base station BS and base station host apparatus OBS, for example.
In this case, logs are sent to the log collecting apparatus LS from
the connector through a cable.
[0227] The log collecting apparatus LS can be embodied by providing
a personal computer with a storage area, such as a hard disk with
large storage capacity or a memory with giga-byte class large
storage capacity, and it has a system in which log information
outputted from the connector is stored in the storage area as a log
collecting button is touched on GUI (Graphical User Interface) in
the display.
A-16. Example of Usage of Reception Level
[0228] The description above has illustrated configurations in
which the reception power (reception level) that the mobile station
receives from base stations is employed as historical information
from the mobile station in order to select handover destinations or
to perform beam control, but the reception level may be employed
not alone but in combination with information about the mobile
station's moving speed.
[0229] FIG. 19 shows an example in which the reception level at the
mobile station and information about the speed of movement of the
mobile station are employed in combination, and FIG. 19 shows an
expression for calculating the reduction of reception level with
respect to the speed of movement of the mobile station.
[0230] In FIG. 19, x denotes the speed of movement of the mobile
station, y denotes the reduction of reception power (a difference
between the reception level at a certain time and the reception
level at the current time), k denotes a predetermined constant, and
z denotes a value "the reduction of reception power divided by the
speed of movement", and FIG. 19 shows a method in which the
reduction of reception power is analyzed according to the relative
magnitude with respect to the constant k.
[0231] In FIG. 19, the reception power is judged to be rapidly
decreasing when the calculated value z is equal to or larger than
the constant k, and it is judged not to be rapidly decreasing when
z is smaller than the constant k.
[0232] When the mobile station is moving away from the base
station, the power that the mobile station receives from the base
station rapidly decreases according to the speed; however, this
cannot be distinguished from a rapid reduction of reception power
caused by a dead spot. However, by dividing the reception power
reduction by the speed of movement, the result of analysis of the
rapid reduction of reception power (z.gtoreq.k in FIG. 19, z(k)
better agrees with the specifying of dead spots.
[0233] Also, the results of analysis can be provided as historical
information from the mobile station to the base station and
employed to control beam from the base station to the mobile
station or to help the base station host apparatus give
instructions to the base station for handover, so as to stabilize
communication.
[0234] Also, the results of analysis as historical information can
be collected as logs in the base station or base station host
apparatus to find dead spots, and then measures can be taken by
raising power of the base station, or very-small-sized base
stations can be newly installed in dead spots, so as to reduce dead
spots.
A-17. Control of Number of Antenna Branches Using Historical
Information
[0235] Now, referring to FIGS. 20 to 24, a system for controlling
the number of antenna branches using historical information will be
described.
[0236] FIG. 20 is a diagram schematically showing that a base
station BS receives historical information from a mobile station MS
and increases/decreases the number of antenna branches used when
the base station BS transmits data to the mobile station MS (or
when it receives data from the mobile station MS).
[0237] The base station BS receives historical information from the
mobile station MS and provides control to increase/decrease the
number of antenna branches. That is to say, for example, when the
mobile station MS sends historical information indicating that the
reception power became small, the number of antenna branches of the
base station BS can be increased to enlarge the power that the
mobile station MS receives. Also, when the mobile station MS sends
a history indicating that the reception power is too large, the
base station BS can reduce the number of antenna branches to lower
the power received at the mobile station to appropriate value. This
reduces power consumption of the base station.
[0238] FIG. 20 shows that the base station BS itself determines to
increase/decrease the number of antenna branches, but the system
may be configured such that a base station host apparatus
determines to increase/decrease the number of antenna branches of
the base station BS on the basis of historical information and
gives instructions to the base station BS to increase/decrease the
number of antenna branches.
[0239] (A-17-1. Configuration of Base Station)
[0240] FIG. 21 is a block diagram illustrating the configuration of
a base station that can increase/decrease the number of antenna
branches on the basis of historical information. The same
components as those of the base station shown in FIG. 11 are
denoted by the same reference characters and not described in
detail again here.
[0241] A data processor block 100A shown in FIG. 21 includes a
demodulator 102, a decoder 103, a historical information obtaining
block 104, an encoder 106, a modulator 107, and a
number-of-antenna-branches determining block 110. The analyzer 105
and the beam forming block 109 shown in FIG. 11 are not shown
here.
[0242] When, in the demodulator 102, historical information is
contained in the control channel of physical channel, the
historical information is extracted in the historical information
obtaining block 104 and given to the number-of-antenna-branches
determining block 110. The number-of-antenna-branches determining
block 110 determines the number of antenna branches required for
the communication with the mobile station, on the basis of
information about the reception power at the mobile station
contained in the historical information.
[0243] When historical information is contained in the data channel
of physical channel and cannot be extracted without channel
decoding and L2 processing, it is given to the historical
information obtaining block 104 through the decoder 103.
[0244] In the case of W-CDMA, for example, when the first 2 bits of
a first transport block of data of 1 TTI (Transmission Time
Interval) form historical information, the historical information
is extracted in the decoder 103.
[0245] When the number of required antenna branches determined in
the number-of-antenna-branches determining block 110 is given to
the modulator 107, weighting values to be multiplied to the signals
corresponding to individual antenna branches are determined to be 0
for antennas not used, and to be 1 for antennas used, so that
signals are validated only for antennas used.
[0246] The number-of-antenna-branches determining block 110 can be
formed of any of CPU, DSP, and FPGA. With DSP, when the historical
information is power value information, the branching processing
can be implemented with a program, e.g. 2 antennas when it is equal
to or more than a certain power value A, 4 antennas when it is
equal to or more than a certain power value B and less than A, and
8 antennas when it is less than the certain power value B. FIG. 22
shows an example in which such a program is generated in C
language.
[0247] By adopting the configuration described above, the base
station can increase/decrease the number of antenna branches on the
basis of historical information from the mobile station. Decreasing
the number of antenna branches reduces the number of high-frequency
components used, such as antenna switches or power amplifiers,
connected to the antennas, resulting in reduction of power
consumption of the components. On the other hand, when the
processing of increasing/decreasing the number of antenna branches
is provided as circuitry in FPGA, the FPGA operates for a longer
time accordingly and power consumption somewhat increases
accordingly; also when it is incorporated as a program in DSP or
CPU, the DSP and CPU operates for a longer time accordingly and
power consumption somewhat increases accordingly; however, such
increase in power consumption is smaller than the decrease in power
consumption, and power consumption can be reduced as a result.
[0248] (A-17-2. Configuration of Base Station Host Apparatus)
[0249] The description above has shown a configuration in which the
base station determines the increase/decrease of the number of
antenna branches on the basis of historical information, but the
system may be configured such that a base station host apparatus
determines the increase/decrease of the number of antenna
branches.
[0250] FIG. 23 is a block diagram illustrating the configuration of
a base station host apparatus that can judge the increase/decrease
of the number of antenna branches on the basis of historical
information.
[0251] As shown in FIG. 23, the base station host apparatus
includes a historical information accumulating block 301, an
analyzer 302, and a number-of-antenna-branches determining block
304.
[0252] When the base station host apparatus receives historical
information (measurement information) as messages, or in the form
contained in data, from a base station, then the historical
information accumulating block 301 extracts and stores the
historical information, and the analyzer 302 analyzes the contents
of the historical information.
[0253] Then, the number-of-antenna-branches determining block 304
determines the number of antenna branches on the basis of the
historical information. In this case, when the historical
information indicates reception level, the determination is made by
using a table in which the number of antenna branches is described
in association with the reception level.
[0254] Then, on the basis of the result of determination in the
number-of-antenna-branches determining block 304, the information
about the number of antenna branches used is transmitted to the
base station communicating with the mobile station, or to a base
station that is to communicate with the mobile station.
[0255] FIG. 24 illustrates a table describing a relation between
the reception level and the number of antenna branches, where the
historical information from the mobile station is the reception
level in the above-described number-of-antenna-branches determining
block 304 and the number-of-antenna-branches determining block 110
shown in FIG. 21.
[0256] As to the reception level, 128 levels, from 0 to 127, of
reception power or reception amplitude are divided into 8 sections
each including 16 levels, and the numbers of antenna branches from
1 to 8 are assigned thereto.
[0257] Larger numerical values of the reception level indicate
larger reception levels, and the number of antenna branches used is
set to be smaller as the reception level becomes larger. Also, the
number of antenna branches used is set to be larger as the
reception level becomes smaller.
[0258] By setting such a correspondence, the number of antenna
branches used can be decreased when the reception level is larger
and can be increased when the reception level is smaller.
[0259] A rougher correspondence may be used in place of the
correspondence as shown in FIG. 24, in which case, for example,
reception levels 111 to 48 are associated with the number of
antenna branches "4", reception levels 127 to 112 are associated
with the number of antenna branches "2", and reception levels 47 to
0 are associated with the number of antenna branches "6". When the
correspondence is set in this way, the number of antenna branches
"4" covers a large range of levels and the number of antenna
branches can be increased/decreased only when the reception level
is at an upper or lower limit; such a configuration is provided for
emergencies where the reception level goes to upper or lower
limit.
[0260] The operation of making determination can be performed at
high speed by using a table as described above; when the scheme is
adopted in the base station host apparatus, the information about
the number of antenna branches can be promptly provided to the base
station after it has obtained historical information from the
mobile station.
A-18. Operation of Analysis in Analyzer
[0261] Next, some examples of the analysis operation in the
analyzer provided in the base station or base station host
apparatus described with FIGS. 11, 14, 21 (not shown), and 22 will
be described.
[0262] (A-18-1. When Using Information about Transmission Rate)
[0263] FIG. 25 shows a table used in the analyzer to determine a
handover destination with information about the transmission rate
when the mobile station is trying to perform a handover or when it
is included in the communication areas of multiple base stations
(not limited to when trying to perform a handover), where the
historical information sent from the mobile station to the base
station includes information about the transmission rate.
[0264] In the table shown in FIG. 25, there are three base stations
(BTS) A, B and C as candidates for handover destination, and the
table contains information about their respective transmission
rates in communications performed in the past within a certain
threshold. That is to say, the transmission rate of the base
station A is 125 kbps and largest, the transmission rate of the
base station B is 78 kbps and smallest, and the transmission rate
of the base station C is 101 kbps and intermediate.
[0265] Accordingly, the analyzer determines the base station A with
the largest transmission rate as the handover (HO) destination.
Alternatively, it determines beam control such that the base
station A directs beam to the mobile station.
[0266] In this way, the analyzer of the base station and base
station host apparatus determines handover destination candidates
or beam control destinations with historical information stored in
the table, whereby the handover destinations or beam control
destinations can be determined with a simple configuration.
[0267] (A-18-2. When Using Information about Number of Unoccupied
Resources)
[0268] FIG. 26 shows a table used in the analyzer to determine a
handover destination with historical information, where, when the
mobile station is communicating with base stations, it provides
base stations with historical information including the numbers of
unoccupied resources (radio resources) of the mobile station
itself, as information about communication condition.
[0269] The mobile station may be connected only with a certain one
base station, or may be connected simultaneously with multiple base
stations, and the data may be used as a reference parameter for
determining the handover destination when the mobile station is
handed over from one base station to another base station.
[0270] When the mobile station is connected only with the base
station C, for example, the mobile station is communicating with
the base station C and provides the base station C with the
historical contents indicating that the number of unoccupied
resources is 5. On the basis of the historical information, the
base station C or base station host apparatus provides control to
raise the transmission rate. As to a configuration for providing
control to raise the transmission rate, in the example of FIG. 11,
for example, a transmission rate controller is provided in place of
the beam forming block 109, and not the modulator 107 but the
encoder 106 is controlled so as to increase the number of resources
used in the mobile station.
[0271] In the example of the base station host apparatus shown in
FIG. 14, the controller 303 provides control to increase the amount
of transmission data. In this case, in the case of W-CDMA, ones
with larger TFCI (Transport Format Combination Indicator) will be
used.
[0272] On the other hand, when the mobile station is simultaneously
connected with multiple base stations, the historical information
from the mobile station is provided to individual base stations and
the numbers of unoccupied resources corresponding to the multiple
base stations are stored in the tables in the analyzers of the base
stations or base station host apparatus.
[0273] That is to say, the table of FIG. 26 stores information
indicating that the number of unoccupied resources is 1 when a
connection is made with the base station A, the number of
unoccupied resources is 3 when a connection is made with the base
station B, and the number of unoccupied resources is 5 when a
connection is made with the base station C.
[0274] From the table, the number of unoccupied resources is
largest when a connection is made with the base station C, so that
the base station or base station host apparatus increases the
amount of downlink data to raise the transmission rate of the base
station C. In case of W-CDMA, a control to increase TFCI is
provided.
[0275] In this case, considering the numbers of unoccupied
resources, the assignment of resources may be dynamically
rearranged according to the historical information; for example,
the number of resources used for the communication with the base
station A is reduced by 2 to increase the number of unoccupied
resources to 3, the number of resources used for the communication
with the base station B is unchanged, and the number of resources
used for the communication with the base station C is increased by
2 to reduce the number of unoccupied resources to 3. The unbalanced
numbers of resources used are thus solved and stable communication
is enabled.
[0276] When the mobile station performs a handover from one base
station to another base station, the historical information is
provided from the mobile station to a base station, and the
historical information about the numbers of unoccupied resources of
other base stations is stored in the table in the analyzer of the
base station or base station host apparatus. In the example of the
table of FIG. 26, the number of unoccupied resources is smallest
when a connection is made with the base station A, and so the base
station or base station host apparatus assumes that the
communication with the base station A is the most stable and
provides control to effect a handover to the base station A.
[0277] Or, some other systems have different ideas about
communication quality and the number of unoccupied resources; when
it is assumed that the resources can be best saved when a handover
is effected to the base station C, the currently communicating base
station or the base station host apparatus provides control to
effect a handover to the base station C. This is a case where the
quality of downlink data from the base station is good on the
mobile station side, but the quality of uplink data from the mobile
station is bad on the base station side. This can happen when the
quality of downlink data received at the mobile station is good,
but the base station side (base station or base station host
apparatus) lowers the transmission rate of downlink data to the
mobile station because the quality of uplink data from the mobile
station is bad, and as a result the number of resources used in the
mobile station is reduced and the number of unoccupied resources
increases.
[0278] In this way, when quality is good but the number of
unoccupied resources is large, the control based on the
notification of historical information to the base station side by
the mobile station raises the downlink transmission rate and raises
throughput, and enables efficient data communication.
[0279] (A-18-3. When Using Information about Increase/Decrease in
Communication Capacity)
[0280] FIG. 27 shows a table used in the analyzer to determine a
handover destination by using historical information, where, during
communication with a base station, the mobile station provides the
base station with historical information indicating
increase/decrease in communication capacity.
[0281] (a) portion of FIG. 7 shows a table with which a base
station or base station host apparatus controls beams when
communication capacity defined by the increase/decrease of the
number of resources and transmission rate is used as historical
information.
[0282] As shown in table of (a) portion, when a decrease in the
number of resources is confirmed in the historical information, the
base station or base station host apparatus provides control to the
base station communicating with the mobile station to direct beam.
Also when a decrease in transmission rate is confirmed, the base
station or base station host apparatus provides control to the base
station communicating with the mobile station to direct beam.
[0283] (b) portion FIG. 27 shows a table with which the base
station or base station host apparatus controls handover when the
communication capacity defined by the increase/decrease in the
number of resources and transmission rate is used as historical
information.
[0284] As shown in table of (b) portion, when it is confirmed in
the historical information that the number of resources increased
when the mobile station communicated with one base station a
certain time ago, the base station or base station host apparatus
instructs that base station to perform handover. Also when an
increase in transmission rate is confirmed, the base station or
base station host apparatus instructs that base station to perform
handover.
[0285] Thus, using increase/decrease in communication capacity as
historical information offers the effects to reduce dead spots and
enable efficient handover.
[0286] Also, the beam control and handover instructions can be
achieved more accurately when the tables of FIG. 27 are
multi-layered, for example, into a short time-width history and a
long time-width history. For example, with the table of (a) portion
of FIG. 27, when the short time-width condition indicates a history
"resources not decreased/transmission rate not became smaller" and
the long time-width condition indicates a history "resources
decreased/transmission rate became smaller", then the weighting
factor is set smaller such that beam is directed not rapidly but
gradually.
[0287] When the short time-width condition indicates "resources
decreased/transmission rate became smaller", the weighting factor
is enlarged to provide control to rapidly direct beam.
[0288] With the table of (b) portion of FIG. 27, in the same way, a
handover is performed when the short time-width condition indicates
"increase/decrease in the number of resources: not increased and
not decreased" and "transmission rate: not changed", and the long
time-width condition indicates "increase/decrease in the number of
resources: increased" and "transmission rate: became larger".
[0289] Also, a handover is performed when the short time-width
condition indicates "increase/decrease in the number of resources:
decreased" and "transmission rate: became smaller", and the long
time-width condition indicates "increase/decrease in the number of
resources: increased" and "transmission rate: became larger".
[0290] Handover is not performed when the short time-width
condition indicates "increase/decrease in the number of resources:
increased" and "transmission rate: became larger", and the long
time-width condition indicates "increase/decrease in the number of
resources: decreased" and "transmission rate: became smaller".
[0291] Forming the historical information in layers enables more
accurate beam control and handover instructions, and offers
significant effects to reduce dead spots and facilitate
handover.
A-19. Variation of Beam Control
[0292] The description above has explained that the beam control of
base stations is performed for the purpose of enabling efficient
handover with mobile stations and to reduce dead spots; but, a
variation as shown below is possible.
[0293] Now, for a judgment of a failure of an adjacent base
station, suppose, for example, historical information about an
adjacent base station exhibited rapid falls of the number of
resources and transmission rate, and an increase in communication
was detected with a base station performing main communication
(interference power suddenly disappeared).
[0294] A mobile station is performing main communication with a
closest first base station and also performing communication with
an adjacent second base station at the same time.
[0295] A mobile station is performing main communication with a
closest first base station and is included also in the
communication area of an adjacent second base station, and it has a
history of communication with the second base station within a
certain time period from an experience of handover.
[0296] With the two cases above, in the former case (simultaneously
communicating with two base stations), the mobile station provides
the historical information from the two base stations to the first
base station or base station host apparatus, whereby the first base
station or base station host apparatus determines a failure of the
adjacent base station.
[0297] That is to say, the second base station, or the adjacent
base station, is judged to have a failure when the historical
information about the second base station indicates rapid falls of
the number of resources and transmission rate and an increase in
communication with the first base station is detected.
[0298] In the latter case (communicating only with one base
station), the history of communication with the adjacent second
base station within a certain time period can be an effective
history when a handover to the second base station was once
conducted but it soon returned to the first base station, and the
first base station or base station host apparatus judges that the
adjacent base station has a failure.
[0299] Then, after the determination of failure was made, the first
base station not suffering a failure performs control to increase
transmission power and direct beam to cover the communication area
of the second base station. That is to say, it performs beam
control to cover the failure.
[0300] In this way, with information from mobile stations, base
stations can find a base station having a failure and provide
control to cover the failure from an adjacent base station.
A-20. Methods of Calculating Transmission Rate
[0301] The mobile communication system MC5 described with FIG. 5
uses transmission rate as historical information, and a first
example of a method of calculating the transmission rate will he
described referring to FIG. 28.
[0302] FIG. 28 shows a transmission rate calculating method for
W-CDMA. In W-CDMA, the transmission rate is obtained by: the number
of TBs (Transport Blocks) minus the number of CRC NGs (error data)
attached to TBs (CRC NG number), or the number of CRC OKs (no-error
data) (CRC OK number), multiplied by the number of bits of TBs per
TTI, and converted into the number of bits per second. In place of
the number of CRC NGs, the number of CRC OKs may be directly
counted without calculating (TB number--CRC NG number).
[0303] The transmission rate can thus be relatively easily
obtained, and the amount of processing is small and high-speed
operation is possible.
[0304] Alternatively, the mobile station may send only the CRC NG
number (or OK number) to the base station as historical
information. In this case, the calculation above is conducted in
the base station or base station host apparatus; the base station
or base station host apparatus can calculate the transmission rate
since they can know parameters, other than the CRC NG number, used
for the calculation, such as TB size. Then the mobile station does
not have to calculate transmission rate and the amount of
processing in the mobile station is reduced, and the mobile station
can send it at high-speed back to the base station as historical
information.
[0305] FIG. 29 shows a second example of a transmission rate
calculating method.
[0306] In W-CDMA, as shown in FIG. 29, the transmission rate can be
obtained by: the number of CRC OKs attached to TBs (CRC OK number)
divided by the number of TBs, multiplied by the maximum possible
transmission rate of that service.
[0307] The actual transmission rate is thus calculated as: the
ratio between the total TB number and CRC OK TB number multiplied
by the maximum transmission rate.
[0308] This calculating method includes a less number of
multiplications than the calculating method described with FIG. 28,
and the amount of processing is reduced and the transmission rate
can be calculated at higher speed.
[0309] Also, as with the calculating method described with FIG. 28,
the mobile station may send only the CRC OK number (or CRC NG
number) to the base station as historical information, in which
case the base station or base station host apparatus can perform
the calculation and the same effects are obtained.
A-21. Notification of Historical Information by User
[0310] (A-21-1. Effects of Notification by User)
[0311] The description so far has illustrated configurations in
which a mobile station measures reception level etc. when receiving
data from a base station and provides the results of measurement as
historical information, or in which a mobile station provides
handover failure information as historical information, where these
operations are automatically performed by functions provided in the
mobile station.
[0312] Now, a configuration will be described below in which a user
sets the current fading environment through GUI or button operation
in the mobile station and the contents are provided to a base
station as historical information.
[0313] FIG. 30 is a diagram illustrating the screen of a mobile
station through which a user sends the current fading environment
to a base station as historical information.
[0314] As shown in FIG. 30, the display DP of a mobile
communication device, such as a mobile phone, as the mobile
station, displays an environment select screen SL for selecting
Indoor, River/Sea, Urban Outdoor, Outdoor (general), Train/Car, and
Shinkansen train, where the user can make arbitrary selection.
[0315] For example, when the user selects "Indoor", the mobile
station sends the information to a base station as the fading
environment where the mobile station is currently positioned. The
historical information is received at the base station or base
station host apparatus; when there is a very-small-sized base
station having an indoor-use cell radius in a room closest to the
mobile station, the base station or base station host apparatus
gives instructions to that base station to communicate with the
mobile station, and the mobile station preferentially connects to
that very-small-sized base station.
[0316] Now, if the mobile station is included in both of the
communication area of a macro-cell base station with a large radius
(around several kilometers) and the communication area of an
indoor-use (home-use) very-small-sized base station with a small
radius (around 10 m) and the mobile station is connected to both,
as in a soft handover condition in W-CDMA, then the base station
host apparatus gives instructions such that the mobile station is
handed over to the very-small-sized base station and communicates
only with the very-small-sized base station, or the communicating
base station gives instructions to the target base station, e.g. to
the macro-cell base station, not to direct beam to the mobile
station.
[0317] Thus, the mobile station can stably communicate with the
very-small-sized base station. Also, the mobile station can be used
as a fixed telephone used only within that house.
[0318] When the user selects "River/Sea", it is possible to realize
operations to eliminate interference waves from far-off stations
since there are fewer obstacles; which will be described later
referring to FIG. 31.
[0319] When the user selects "Urban Outdoor", the mobile station
provides the information to the base station as the fading
environment where the mobile station is currently positioned.
"Urban Outdoor" assumes a place surrounded by buildings or in an
office in a building. When there are many dead spots and
very-small-sized base stations having cell radiuses of several to
several tens of meters are installed in such dead spots, the
currently communicating base station or base station host apparatus
gives instructions to other base stations such that those other
base stations will not direct beam to the mobile station or not to
effect handover when the mobile station is communicating with such
a very-small-sized base station.
[0320] This prevents the user from being suddenly subjected to
interference waves from a macro-cell base station, e.g. when the
user was behind a building and walked just some steps out from
behind the building. However, when the quality of communication
with the very-small-sized base station deteriorates, the other base
station or base station host apparatus stops the control of
preventing other base stations, other than the very-small-sized
base station, from directing beam to the mobile station or from
effecting handover.
[0321] When the user selects "Outdoor (general)", the mobile
station provides the information to the base station as the fading
environment where the mobile station is currently positioned.
"Outdoor (general)" assumes the general outdoor with relatively few
obstacles, such as a residential area.
[0322] For example, when a home-use very-small-sized base station
is provided in a house in a residential area, the radio waves from
the very-small-sized base station serve as interference waves for a
user walking around the house. This is because the mobile station
is in an overlap of the communication area of a macro-cell base
station and the communication area of the home-use very-small-sized
base station.
[0323] Accordingly, when the user is staying outdoors, the
historical information of "Outdoor (general)" is provided to the
currently communicating macro-cell base station, and the base
station or base station host apparatus provides control such that
the very-small-sized base station will not direct beam to that
mobile station, or such that it will not connect to that mobile
station, e.g. by preventing assignment of resources.
[0324] Thus, for the mobile station staying outdoors, interference
waves from the very-small-sized base station provided indoors are
reduced. This control operation is possible because the
very-small-sized base station subjected to the control temporarily
comes in a handover condition with the mobile station and the base
station host apparatus can therefore identify that very-small-sized
base station.
[0325] Even when the mobile station communicates with the
very-small-sized base station before the user selects "Outdoor
(general)" and cannot return to the communication with the
macro-cell base station, it is possible to enable it to return to
the communication with the macro-cell base station when this
selection is made, as the very-small-sized base station controls
itself, or as the base station host apparatus controls the
very-small-sized base station, such that the very-small-sized base
station will not direct beam.
[0326] When the user selects "Train/Car" and selects "Car", the
display DP of the mobile station displays a screen in which the
destination can be set, like a car navigation system, and the user
inputs the destination; then, the base station or base station host
apparatus gives instructions to base stations that are to
communicate with the mobile station (or base stations that are not
to communicate) such that the mobile station can be handed over to
most appropriate base stations as it moves, or such that most
appropriate base stations will direct beam thereto. Thus, the
mobile station can always communicate only with the most
appropriate base stations.
[0327] Similarly, when "Train" is selected, the display DP of the
mobile station displays a screen in which the destination station
etc. can be set, and the user sets the destination station; then
the base station or base station host apparatus gives instructions
to base stations that are to communicate with the mobile station
(or base stations not to communicate) such that optimum handover
and beam control can be achieved.
[0328] When the User selects "Shinkansen train" and sets the
destination station and the start and arrival times of the target
Shinkansen train in a manner similar to those of "Train", the
mobile station provides the information to the base station; then,
on the basis of the information, the base station or base station
host apparatus gives instructions to base stations that are to
communicate with the mobile station (or base stations not to
communicate) such that optimum handover and beam control can be
achieved.
[0329] "Shinkansen train" is independently identified because it
moves at particularly high speed and the mobile station is handed
over to a large number of base stations. For example, when it is in
connection with one base station before it comes into a tunnel, it
stays in connection with the same base station while it is inside
the tunnel, but radio waves from another base station placed
forward of the tunnel suddenly become intensive when it comes out
of the tunnel; the radio waves serve as interference until it is
handed over, and then transmission power control, present in
W-CDMA, for example, will not work and the connection may be
broken.
[0330] In order to avoid such a problem, the base station placed
forward of the tunnel is controlled for a while after the mobile
station came out of the tunnel such that the base station lowers
the transmission power to the mobile station and raise power
gradually, for example.
[0331] When a base station or an antenna of a base station is
provided inside a tunnel, a mobile station moving at the speed of
Shinkansen train is controlled to be handed over to the base
station (the base station's antenna) as early as possible before it
comes into the tunnel.
[0332] When a mobile station is inside a tunnel and then goes out
of the tunnel, it is controlled to be handed over to a base station
out of the tunnel as early as possible.
[0333] The base station out of the tunnel is controlled such that
it directs beam to the mobile station while the mobile station is
inside the tunnel, and such that it weakens the power of beam
toward the mobile station for a while after the mobile station came
out of the tunnel so that the power received at the mobile station
will not rapidly rise.
[0334] Such control is enabled when "Shinkansen train" is selected,
and the mobile station can stably communicate with base stations as
optimum handover control and beam control are possible while it is
traveling on the Shinkansen train.
[0335] Also, when the mobile station informs the base station that
it is on the Shinkansen train as historical information, the base
station or base station host apparatus can know the speed of
movement of the mobile station. Then, it is possible to
appropriately perform reception processing in the base station (in
averaging with a loop filter during demodulation, the time constant
can be optimized to the high moving speed of the Shinkansen train,
for example), and to appropriately perform handover, beam forming,
etc. according to that fading environment, whereby communication
quality is enhanced and communication can be performed stably.
[0336] For another measure, during high-speed movement like when
"Shinkansen train" or "Train" is selected, it is also effective to
reduce the number of averaging operations of the reception power in
the demodulator so that path can be detected quickly.
[0337] In this way, when the user enters the fading environment, it
is possible to relatively easily achieve control operations
suitable for the environment where the mobile station is
placed.
[0338] (A-21-2. Operation when "River/Sea" is Selected)
[0339] Next, referring to FIG. 31, an example of operation
performed when the user selects "River" will be described.
[0340] In FIG. 31, when a mobile station 11 communicating with a
base station A moves to the river RV where fewer obstacles are
present, it receives radio waves from a base station C that it did
not receive before moving. The communication area C1 of the base
station C exists along the river RV, and the mobile station 11
enters the communication area 11 only when it is present in the
river RV; the radio waves from the base station C do not reach when
the mobile station 11 goes away from the river RV. On the other
hand, the communication area A1 of the base station A covers a
large area including the river RV, and the communication area B1 of
a base station B also covers an area near the river RV.
[0341] In such a case, there is no need to communicate with the
base station C because even if the mobile station is handed over to
the base station C, it will soon be returned to the communication
with the base station A, or will soon be handed over to the
communication with the base station B. Accordingly, the radio waves
from the base station C can be regarded as interference waves.
[0342] When the user operates the screen to set that the mobile
station 11 is currently in the river, the mobile station 11
provides that environment information to the base stations A and C.
Then, a base station or base station host apparatus gives
instructions such that the base station C will not communicate with
the mobile station and not direct beam thereto. Then, the mobile
station 11 is less likely to be influenced by the interference
waves from the base station C even when it is in the river. The
same effect is obtained not only when it is in a river but also
when it is in a broad street.
[0343] (A-21-3. Automatic Acquisition of Environment with Condition
Notifying Servers)
[0344] Next, a configuration will be illustrated where the
environment of the mobile station can be automatically obtained
even when the user does not select the environment like
"River/Sea".
[0345] Like FIG. 31, FIG. 32 is a diagram showing a mobile station
11A in the vicinity of the river RV. As shown in FIG. 32, condition
notifying servers 16 (local servers), which notify the mobile
station 11A that it is in the river, are provided along the river
RV, and they notify the mobile station 11A that it is in the river
RV when it enters their communication areas. Accordingly, the
mobile station 11A can automatically know its environment even when
the user does not enter information from the environment select
screen etc.
[0346] The mobile station 11A provides the obtained environment
information to the base stations A and C, and the mobile station
11A is subjected to less interference from the base station C as
described with FIG. 31, and can perform stable communication.
[0347] Such condition notifying servers 16 can be employed not only
near rivers but also in indoor areas, cars, trains, and Shinkansen
trains, whereby the mobile station 11A can automatically obtain
information about its environment etc. and send the information to
base stations.
[0348] Also, the function of the condition notifying server may be
contained in a very-small-sized base station (which may be provided
indoors or outdoors); also, condition notifying servers may be
provided in vehicles such as Shinkansen trains, other trains, or
cars; when a mobile station gets on such a vehicle, the mobile
station can be informed from the condition notifying server in the
vehicle that it has got on the vehicle, and it can send the
information to base stations as historical information.
[0349] The configuration of the condition notifying servers 16 will
be illustrated referring to the block diagram of FIG. 33.
[0350] As shown in FIG. 33, the condition notifying server 16
includes a ROM (Read Only Memory) 162 that stores information
(environment information) corresponding to historical information,
a D/A converter 161 that converts digital signal read from the ROM
162 and outputs analog signal, an antenna 160 that sends out the
analog signal outputted from the D/A converter 161, and a connector
163 that connects the ROM 162 to external equipment.
[0351] A modulator may be provided between the ROM 162 and the D/A
converter 161. In this case, a demodulator is provided in the
receiving mobile station.
[0352] In order to prevent tempering of environment information,
the environment information may be encrypted. In this case, in the
configuration of FIG. 33, an encrypting block is provided between
the ROM 162 and the D/A converter. A decrypting block is provided
in the receiving mobile station.
[0353] Thus, the condition notifying server 16 can take a simple
configuration, and the costs of digital signal boards etc. can be
low; also, low-priced high-frequency transmission equipment etc.
can be used when it is designed for operations within short
distances (around 20 to 30 meters). Also, it can be mass-produced
(mass-ordered) products when they are installed in a large number
of places, and individual devices including the ROM 162, connector
163, and D/A converter 161 can be lower-priced and the entire
condition notifying server 16 can be low-priced and can be
installed at low costs.
[0354] Also, when the condition notifying server 16 stores detailed
information about the position, it is possible to know through a
base station or base station host apparatus how the mobile station
11A moved.
[0355] FIG. 34 is a block diagram illustrating the configuration of
a mobile station 11A that can receive environment information from
the condition notifying server 16 shown in FIG. 33.
[0356] The data processor block 200A shown in FIG. 34 has basically
the same configuration as the data processor block 200 of the
mobile station 11 described with FIG. 12, and the operations of
processing data exchanged with base stations are the same; but it
further includes an antenna AT3 for receiving notifications from
the condition notifying server 16, a radio section RX3 for
down-converting the signal received at the antenna AT3 to generate
a baseband signal, an A/D converter 211 for A/D converting the
baseband signal, an environment information receiving block 209 for
analyzing the environment information converted to digital signal,
and an environment information storage block 210 for storing the
environment information.
[0357] The environment information receiving block 209 analyzes
information by referring to a table that defines, for example, data
"1" as presence in a river, data "2" as presence indoors, etc.
[0358] When the environment information signal is modulated, a
demodulator may be provided between the environment information
receiving block 209 and the A/D converter 211 as stated above, and
a decrypting block may be provided between the environment
information receiving block 209 and the A/D converter 211 when the
environment information signal is encrypted.
[0359] The environment information stored in the environment
information storage block 210 is inserted into data from an upper
layer, or inserted in the format in the encoder 206, or
bit-inserted in the control channel of physical channel in the
modulator 207 (in the case of W-CDMA, an area for storing
historical information is provided in DPCCH).
[0360] The mobile station 11A thus configured can automatically get
information from the condition notifying servers 16 about where the
mobile station 11A is currently present and in what environment it
is present, and it can provide that information to a base station
or a base station host apparatus through a base station.
A-22. Method of Calculating Transmission Rate
[0361] The mobile communication system MC4 described with FIG. 4
employs the speed of movement of the mobile station as historical
information; a method of calculating the speed of movement will be
described referring FIGS. 35 to 37.
[0362] FIG. 35 is a diagram illustrating a mobile communication
system in which the historical information provided from the mobile
station 11 to the base station side is "high speed" of movement of
the mobile station.
[0363] As shown in FIG. 35, the mobile station 11 is communicating
with the base station A, and moving at high speed toward the base
station B. In the middle between the base station A and the base
station B, it enters the communication area B1 of the base station
B and goes into a handover condition from the base station A to the
base station B.
[0364] In this case, on the basis of the historical information,
indicating high speed movement, provided from the mobile station 11
to the base station A or the base station B, the base station or
base station host apparatus (network) instructs the base station A
and the base station B to direct beam to the mobile station 11 such
that the communication areas overlap as long as possible so that
the handover can take longer time.
[0365] Then, the mobile station 11 does not have to complete the
handover in haste even when it is moving at high speed, and the
possibility of handover failure is reduced.
[0366] FIG. 36 is a flowchart illustrating a procedure for
obtaining the moving speed in the mobile station 11; in the
configuration of the mobile station 11 shown in FIG. 12, this
calculation is performed in the demodulator 202 or measurement
block 205.
[0367] First, in a reception level measuring block in the
demodulator 202, the intensity of signal power that the mobile
station 11 receives from the base station is measured (Step S1). In
this case, signal power may be divided into levels and obtained as
a reception level.
[0368] The reception level thus obtained is given to a notch
detecting block in the demodulator 202, and whether the level falls
down is determined (Step S2). When the falls are judged to be
fading notches (falls of power), the notch cycle is detected
next.
[0369] Then, in a moving speed estimating block in the demodulator
202, the speed of movement is estimated by referring to a table
that associates the notch cycle, information such as radio
frequency, band, etc. and the speed of movement (which can be
maximum Doppler frequency). The mobile station can thus estimate
the speed of movement.
[0370] The notch detection can be obtained from the degree of
signal distortion and the deterioration of reception level. That is
to say, the degree of signal distortion can be calculated using the
principle shown in FIG. 37 when the amplitude of I and the
amplitude of Q of the reception signal are known.
[0371] The magnitude of the amplitude of received signal is divided
into levels, and the reception level is obtained, for example, as
level 3 from one value to another value, as level 17 from one value
to another value, and so on.
[0372] The degree of signal distortion is obtained, for example,
with the square sum of "I component (real part)" (known signal is
1+0.times.j and so a difference with subtraction of 1) and "Q
component (imaginary part)", and the distortion is judged to be
large when the value is 0.7 or larger.
[0373] That is to say, the signal is represented with a complex
number, and when the known signal (one of pilot symbols in the case
of W-CDMA) is 1+j.times.0, it is plotted in FIG. 37 in the position
of point R at the end of the thick line on I axis.
[0374] On the other hand, in FIG. 37, the reception signal
(distorted signal) is plotted in the position of point P at the end
of thin line in the quadrant defined by I axis and Q axis. The
phase difference and amplitude difference between the two are the
signal distortion, and the position of point Pin FIG. 37 is
1.1+j.times.0.9 and the degree of distortion is
1.1+j.times.0.9.
[0375] In this way, in the notch detecting block in the demodulator
202, the degree of signal distortion is first obtained, and in
combination with the reception level, notch is judged to be
detected when the degree of signal distortion is large and
reception level is low.
[0376] The reception level is divided into levels 0 to 127. for
example, and the reception level is judged to be low when it is
level 10 or below.
[0377] The notch detecting block and moving speed estimating block
are both formed of DSP or FPGA.
[0378] Whether the calculated moving speed is high speed or not can
be obtained by conditional branching by referring to the table of
FIG. 38.
[0379] That is to say, the speed is handled as being low when it is
less than 40 km/h, as being intermediate when 40 km/h or more and
less than 80 km/h, as being middle high when 80 km/h or more and
less than 200 km/h, and as being high when 200 km/h or more.
[0380] (A-22-1. Another Example of Method of Calculating
Transmission Rate)
[0381] In place of the method shown in FIG. 36, the speed of
movement may be obtained by comprehensively considering the history
of received field strength, estimated transmission path
characteristic (CIR) calculated in the mobile station, reception
power (in the case of W-CDMA, constant-power common channel from
base stations), frequency deviation, delay profile movement. etc.,
for example. In this case, when the received field strength or
reception power from one base station became gradually larger, the
approaching speed is judged to be slow, and when such value is
becoming smaller rapidly, the separating speed is judged to be
high, for example.
[0382] As to CIR, a judgment can be made according to how much the
CIR deviates from 1+0.times.j, and the speed of movement can be
judged to be large when the phase rapidly rotates, and can be
judged to be small when the phase gradually rotates.
[0383] Also with frequency deviation, the speed of movement is
judged to be large when the deviation rapidly becomes larger
(smaller), and the speed of movement can be judged to be small when
the deviation gradually becomes larger (smaller).
[0384] As to the movement of delay profile position, the speed of
movement can be judged with the rate of movement of the largest
correlation position. The speed of movement may be judged according
to a combination of the factors, or the speed of movement may be
comprehensively judged by combining them and that obtained from
fading notch.
[0385] Also, the speed of movement can be roughly estimated by
forming the history table of FIG. 15 in multiple layers, i.e. in a
short time width (e.g. per 666 .mu.s) history and a long time width
(e.g. per 20 ms) history. That is to say, when the variations are
small in the 666 .mu.s-width history but the variations are
intermediate in the 20 ms-width history, it can be estimated as
moving at low speed. Also, it can be estimated as moving at high
speed when the variations are large in the 666 .mu.s-width history.
The speed of movement of the mobile station can be simply estimated
without complicated calculations by adopting such an estimation
method.
[0386] As described above, the precision of the estimation of
moving speed can be enhanced by obtaining the moving speed on the
basis of a large number of measurement results.
B. Second Preferred Embodiment
[0387] A mobile communication system according to a second
preferred embodiment of the present invention is characterized in
that a mobile station transmits/receives different data to and from
different base stations in a mobile communication system where the
mobile station can communicate simultaneously with a plurality of
base stations.
[0388] FIG. 39 illustrates the configuration of the mobile
communication system according to the second preferred
embodiment.
[0389] In FIG. 39, a plurality of base stations 362, 363, 364 and
365 are connected to a base station host apparatus 361. The
connections with the base stations can be either wireless or wired.
The base stations 362 to 365 communicate with a mobile station 366
by radio.
[0390] Next, the operation will be described referring to FIG.
39.
[0391] In FIG. 39, the mobile station 366 is communicating
simultaneously with the base stations 363 and 364. In this case,
the mobile station 366 exchange different data with the base
stations 363 and 364.
[0392] As to the method of transmission/reception of different
data, when the mobile station performs radio transmission by OFDM
in the data transmission from the mobile station to the base
stations, it can transmit data A to the base station 363 by using
one sub-carrier, and transmit data B to the base station 364 by
using a bus-carrier not used for the transmission of data A.
[0393] On the other hand, in the transmission from the base
stations to the mobile station, when the base stations employ
single carrier transmission, the base stations 363 and 364 transmit
respective data to the mobile station 366, and the mobile station
366 can receive the data by multi-carrier transmission such as OFDM
by using different sub-carriers, e.g. by receiving data from the
base station 363 with a sub-carrier No. 1, and receiving data from
the base station 364 with a sub-carrier No. 2.
[0394] Thus, a larger amount of data can be transmitted than when
the mobile station 366 exchange same data with the base stations
363 and 364.
[0395] It is also possible to divide one data sequence into
multiple data pieces and transmit them to different base stations.
An example of operation in such a case is illustrated in FIG.
40.
[0396] FIG. 40 is a flowchart illustrating a method of dividing and
coupling data respectively in channel coding and channel
decoding.
[0397] FIG. 40 shows a method of channel decoding where the mobile
station 366 receives different data respectively from the base
stations 363 and 364.
[0398] As defined in 3GPP TS25.212, for example, the channel
decoding is to convert from a frame format suitable for the
physical layer into a format suitably for an upper layer.
[0399] In FIG. 40, when data from the base station 363 is inputted
(Step S10), it is converted into a radio channel format (Step S11).
Similarly, when data from the base station 364 is inputted (Step
S13), it is converted into a radio channel format (Step S14).
[0400] In the process of conversion into data format, the radio
channel format is divided into a control channel format storing
control information inherent to the base station and a data channel
format sent to the upper-layer equipment.
[0401] Then, the control channel format received from the base
station 363 is separated as control information for the base
station 363 including signal congestion condition etc. (Step S12),
and the control channel format received from the base station 364
is separated as control information for the base station 364
including signal congestion condition etc. (Step S15).
[0402] On the other hand, as to the data channel format, the data
format received form the base station 363 and the data channel
format received from the base station 364 are coupled and
channel-decoded into one data sequence (Step S16). Data pieces
passing through different transmission paths are thus combined;
therefore, even if one transmission path is distorted, it can be
corrected if the distortion of the other transmission path is
small, and the mobile station can thus receive data with stronger
error correcting capability.
[0403] In FIG. 40, data is processed through the opposite course to
that shown in FIG. 40 when data is transmitted from the mobile
station 366 to the base stations 363 and 364.
[0404] That is to say, when the mobile station 366 transmits one
data sequence to different two base stations 363 and 364, the
channel coding is performed in the course opposite to that shown in
FIG. 40.
[0405] During the process of channel coding, the data format is
divided into two data formats, and coupled with respective control
formats including information such as resource specify information
for the base stations 363 and 364 and information about
transmission power from the base stations 363 and 364 to the mobile
station 366, and they are converted to radio channel formats and
transmitted respectively to the base stations 363 and 364.
[0406] The data from the mobile station are received at the base
stations and channel-decoded after transmitted to the base station
host apparatus, and the data are thus decoded into one data format;
or, when the base stations are connected with each other, data are
received from the base stations 363 and 364, and the base station
363, for example, performs channel-decoding to decode one data
sequence.
[0407] When the method above is adopted, and when only the
transmission path between the mobile station 366 and the base
station 363 is bad and so data transmission has failed, and the
mobile station 366 received a retransmission request from the base
station 363, then the mobile station 366 can transmit data (to be
transmitted to the base station 363) not to the base station 363
but via the base station 364. The data to be transmitted to the
base station 364 has been already successfully transmitted, and
therefore only the divided half data sequence is retransmitted
without the need to retransmit all data sequence, and the data
retransmission by radio can be achieved at high speed.
[0408] Such historical information as described in the first
preferred embodiment may be contained in place of the control
information in the control channel formats.
C. Third Preferred Embodiment
[0409] The mobile communication systems described in the first
preferred embodiment of the present invention have a configuration
in which the mobile station provides historical information to base
stations, but it is possible to adopt an opposite configuration in
which base stations provide historical information to the mobile
station and the mobile station directs beam to base stations and
performs handover on the basis of the historical information.
[0410] FIG. 41 illustrates the configuration of a mobile
communication system MC20 according to a third preferred
embodiment.
[0411] In the mobile communication system MC10 shown in FIG. 41, a
base station 12, a base station 13, and a base station 15 are
connected to a base station host apparatus 14.
[0412] A mobile station 11 is moving toward the base station B,
currently included in the respective communication areas A1, B1,
and C1 of the base stations A to C, and is in a handover condition
and simultaneously connected with the base stations A to C.
[0413] In this case, the base stations A to C provide the mobile
station 11 with historical information (measurement information)
including the power of signals received from the mobile station 11
and SIR (uplink SIR of reception at the base stations); receiving
the historical information, the mobile station 11 knows the
direction of movement of the mobile station 11 on the basis of
information indicating that SIR or power is becoming larger or
smaller. For example, the mobile station 11 directs beam to the
base station B at the time when the historical information about
SIR or power from the base station B reaches a certain value. This
enables a handover with appropriate timing.
[0414] The mobile station 11 can easily determine to which base
station it should direct beam, e.g. by generating a table shown in
FIG. 42.
[0415] That is to say, FIG. 42 shows an example in which historical
information from the base stations A to C are captured at certain
times (e.g. with counting by a counter provided in the mobile
station 11) and a list is generated.
[0416] According to FIG. 42, the information about SIR from the
base station A captured at counts 1 to 4 indicates 15 [dB], 7 [dB],
3 [dB] and -3 [dB]. Also, the information about SIR from the base
station B captured at counts 1 to 4 indicates 0 [dB], 6 [dB], 11
[dB] and 19 [dB]. Also, the information about SIR from the base
station C captured at counts 1 to 4 indicates 4 [dB], 6 [dB], 4
[dB] and 3 [dB].
[0417] On the basis of the table thus generated, the mobile station
11 judges that it is moving from the base station A toward the base
station B because the SIR information from the base station B is
becoming larger with time, and it operates to effect a handover
according to a predetermined rule that it directs beam to the base
station B when the historical information from the base station B,
positioned in the direction of advance, exceeds 10 [dB]. It is also
possible to tune to more suitable handover timing by setting the
beam directing threshold to a value other than 10 [dB].
[0418] FIG. 43 illustrates the configuration of a base station for
implementing a system in which the base station generates
historical information and provides it to the mobile station. In
FIG. 43, the same components as those of the base station of FIG.
11 are shown by the same reference characters and not described
again here.
[0419] As shown in FIG. 43, the base station has a history
processing block 120 in the data processor block 100B, where
historical information processed in the history processing block
120 is given to the modulator 107 or encoder 106 and multiplexed
and transmitted with downlink transmission data.
[0420] The history processing block 120 has a configuration similar
to that of the historical information storage block 204 and the
measurement block 205 of the mobile station described with FIG. 12;
it measures SIR of signal from the mobile station 11, once stores
the measured value, and then gives it as historical information to
the modulator 107 or encoder 106.
[0421] FIG. 44 illustrates the configuration of the mobile station
that receives the historical information generated in the base
station. In FIG. 44, the same components as those of the mobile
station shown in FIG. 12 are shown with the same reference
characters and not described here again.
[0422] As shown in FIG. 44, the mobile station includes a
historical information obtaining block 220, an analyzer 230, and a
beam forming block 240 in the data processor block 200B, where the
analyzer 230 analyzes the contents of historical information from
the base station, and when beam control is to be performed, the
beam forming block 230 performs weighting control etc.
[0423] The historical information obtaining block 220, the analyzer
230, and the beam forming block 240 have the same configurations as
the historical information obtaining block 104, the analyzer 105,
and the beam forming block 109 of the base station described with
FIG. 11.
[0424] Like a system in which mobile stations' historical
information is provided to base stations, such a system in which
base stations' historical information is provided to mobile
stations offers the effects to enhance communication quality and
eliminate interference through handover and beam control.
[0425] The description above has illustrated a configuration in
which information about communication quality and communication
condition with a mobile station, measured in base stations, is
provided as historical information to the mobile station, but a
configuration is possible in which information about communication
quality and communication condition with a mobile station, measured
in the base station host apparatus 14, is provided as historical
information to the mobile station. In such a case, the base station
host apparatus 14 adopts a configuration as shown in FIG. 43.
[0426] While the invention has been described in detail, the
foregoing description is in all aspects illustrative and not
restrictive. It is understood that numerous other modifications and
variations can be devised without departing from the scope of the
invention.
* * * * *